Swell Matrix

Area Forecast Discussion

National Weather Service San Francisco CA

940 pm PDT Sun aug 9 2026

Short Term

, Issued at 1212 PM PDT Sun Aug 9 2026 (This evening through Monday night)

A more compressed marine layer allowed for rapid clearing of stratus to the immediate coastline late this morning. As such, have left the Heat Advisory in place for much of the interior Bay Area and Central Coast through 10 PM this evening. However, locations under the around 500-800 foot marine layer may struggle to reach their afternoon maximum forecast temperatures. This is especially so around the San Jose region, yet the southern Santa Clara Valley has the potential.

Minor coastal flooding is also expected around the time of the highest high tide (evening/overnight) for bayshore locations along the San Francisco Bay, San Pablo Bay, and Monterey Bay through Thursday morning. The decision not to include the Pacific Coast was made yesterday evening when the forecast fell below the predicted values, yet still high enough to maintain the aforementioned bays. Please see the CFW product we have out for additional details. Also, for more on the fire weather concerns through early in the week, please see the Fire Weather Section of the AFD below.

During this weekend's heat event, remember:

* Stay hydrated and drink plenty of fluids. * Wear lightweight and light-colored clothing. * Reduce time spent outdoors or stay in the shade. * Never leave people or pets unattended in vehicles. * Use sunscreen if going to the coast or the pool.

Afternoon temperatures are forecast to cool some 5-10 degrees on Monday as a weak shortwave trough develops off of the West Coast. As such, HeatRisk levels lower to minor with pockets of moderate.

Long Term

..issued at 1212 PM PDT Sun Aug 9 2026 (Tuesday through next Saturday)

The troughing would also support coastal drizzle and/or mist each night and morning through late week. Temperatures cool to below normal (as much as 20 deg F below by Friday) as a reinforcing upper level through develops off of the Bay Area and Central Coast. As this low pressure approaches the coastline late in the week and monsoonal moisture advects northward around the high over the Four Corners, there is the potential for high-based convection. There remains a great deal of uncertainty of whether or not there will be enough instability aloft to support thunderstorms. While this is still far out in time and low confidence, any dry lightning would be problematic from a fire weather standpoint. Be sure to check back for additional details as we move closer to midweek.

Aviation

(06z TAFS) Issued at 929 PM PDT Sun Aug 9 2026

Currently VFR except for KHAF and the Monterey Bay terminals. Expect primarily onshore flow, however offshore eddy's are complicating the inland push of the stratus, producing short windows of local offshore flow. Should see MVFR/IFR ceilings materialize after midnight and persist through at least late morning.

Vicinity of SFO, Offshore eddys should continue to complicate the exact timing of MVFR/IFR ceilings until after midnight. Given the uncertainty of how much the eddys will impact how well organized the marine layer is, maintained late morning clearing instead of early afternoon indicated by some guidance.

SFO Bridge Approach, Similar to SFO.

Monterey Bay Terminals, MVFR ceilings have developed over both terminals and will persist through late morning with breezy onshore flow. VFR through the remainder of the afternoon and early evening with MVFR/IFR stratus ceilings returning near sunset.

Marine

(tonight through next Saturday) Issued at 929 PM PDT Sun Aug 9 2026

Fresh to strong northwest winds will persist through the middle of the week with rough seas up to 12 feet over the northern outer waters and occasionally the inner waters north of Point Reyes. The San Pablo, Suisun Bays and the Delta will continue to see gusty onshore winds through early Monday evening. The long period southerly swells around 15 seconds will continue through much of the work week.

Watches, Warnings, Advisories

Ca, Coastal Flood Advisory until 2 AM PDT Thursday for CAZ006-506- 508-529-530.

Heat Advisory until 10 PM PDT this evening for CAZ503-504-510- 512>518.

PZ, Small Craft Advisory until 3 AM PDT Tuesday for SF Bay N of Bay Bridge.

Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt Reyes 0-10 nm.

Small Craft Advisory until 9 AM PDT Wednesday for Pt Arena to Pt Reyes 10-60 NM.

Visit this site often? Consider supporting us with a $10 contribution.
Learn more