textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 753 PM PDT Sun Oct 18 2026

- Cooling trend continues through the end of the week

- Beneficial light rain showers expected mid-week

- Thunderstorms possible mid-week across southern Central Coast

UPDATE

Issued at 753 PM PDT Sun Oct 18 2026

The cooler weather has arrived! Across the Bay Area and Central Coast, temperatures dropped 10-20 degrees within the last 24 hours with some spots experiencing up to a 30 degree drop. Accompanied with the lower temperatures is an increase in humidity. The marine layer has reformed with a current depth around 1500-2000 feet. Moderate, gusty onshore winds will help push stratus further inland tonight. So, enjoy the stratus while you can because it won't last long! Tomorrow, temperatures are expected to drop another 10-20 degrees with gusts around 20 mph. Breezier locations may experience gusts up to 30-35 mph which gradually diminish Monday evening.

SHORT TERM

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.

LONG TERM

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.

AVIATION

(06Z TAFS) Issued at 1001 PM PDT Sun Oct 18 2026

MVFR stratus is building into the valleys of the greater SF Bay Area and patches around Monterey Bay with further expansion expected overnight. Clearing times Monday morning and afternoon will be rather late owing to an incoming trough that will lower temperatures and expand the marine layer. Gentle to moderate onshore winds will persist through Monday evening, when winds diminish and turn southerly. Low confidence in the stratus extent and ceilings beginning on Monday night owing to potential mixing out of the lower layers as the trough approaches. Any rain chances from the incoming trough come later on Tuesday, after the TAF period ends.

Vicinity of SFO... MVFR ceilings persist through Monday morning. Moderate northwest winds will continue through Monday evening with strong gusts expected in the afternoon and evening hours with a more southerly component as the winds diminish Monday evening. Low confidence for stratus returning to the terminal Monday night.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... MVFR ceilings at the terminals will clear late Monday morning or early afternoon. Gentle to moderate northwest winds prevail through Monday evening, with light southerly flow developing Monday night.

MARINE

(Tonight through next Saturday) Issued at 1001 PM PDT Sun Oct 18 2026

Moderate to fresh northwesterly breezes will prevail through Monday, with hazardous conditions for small craft lingering at the inner coastal waters south of Pigeon Point through Monday morning. 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 Monday, rebuilding to become rough Tuesday. Light rain showers are expected Tuesday through Thursday.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory until 3 AM PDT early this morning for Pigeon Pt to Pt Pinos 0-10 nm.

Small Craft Advisory until 9 AM PDT this morning for Pt Pinos to Pt Piedras Blancas 0-10 nm.