Swell Matrix

Area Forecast Discussion

National Weather Service San Francisco CA

415 am PDT Sat may 9 2026

Short Term

, Issued at 1130 PM PDT Fri May 8 2026 (Tonight through Sunday)

The building ridge has called for much less stratus coverage than previous nights as the marine layer compresses. Cloud cover will still be prevalent along the coast, but will be spottier in the Bays and the inland areas. Pockets of fog will still be possible, but look to also be spottier than previous nights. Temperatures will still be close to average through the night with lows in the upper 40s to low 50s.

Saturday continues the warming trend due to the weaker marine influence, reduced cloud cover, and building ridge. Many more of the inland areas to break into the 80s, while coastal areas will stay low 60s, and the slightly inland areas stay in the 70s, but most areas away from the coast look to break 80. A few of the more inland areas look to break into the mid 90s than previous days.

Saturday night will have slightly warmer temperatures and comparable marine layer conditions to Friday night/Saturday morning. However, the slights more compressed marine layer into Sunday morning will cause the overall moisture to be more denser within the marine later. This will offer better chances for early morning fog in the favored valleys.

The compression of the marine layer and building of the ridge continues Sunday leading to temperatures to increase by another few degrees in the inland areas, while the coast remains cool in the 60s with the help of a good sea breeze and shallow marine layer.

Long Term

..issued at 1130 PM PDT Fri May 8 2026 (Sunday night through next Friday)

While the marine layer stays intact for Sunday night, the inland push of stratus looks to be very modest. Again, valleys will see good chances for fog early Monday, but fog looks to mix out by the mid morning. The increasing pressure from the ridge will begin to form a thermal belt, causing higher peaks to see limited overnight cooling with lows in 60s and a few 70s.

Monday is set to be hottest day of the forecast. The ridging patter peaks and most of the winds become light for a large portion of the region. Most of the interior valleys look to break into the 90s with widespread 80s for all but the near-coastal areas seeing the 60s and 70s. Those higher peaks affected by the thermal belt look to jump into the 90s as well with the warm morning lows giving them a head start.

The ridge begins to push east, allowing for good cooling Monday night as the thermal belt collapses, and a notable cooldown Tuesday. However, Tuesday will still be on the hot side, offering temperatures similar to Sunday.

From there, models continue to have a bit of a split in the movement of an approaching trough. The ECMWF and GFS model and ensemble families have the trough and its embedded low pass through the Bay Area and most of Northern California. This will offer drizzly conditions and much cooler conditions. But models differ on the timing, with some calling for this change in the mid week, while others slow it way down and hold off until the end of the work week. Another possible solution is that the low stays north, preventing the drizzle chances, and only offering modest cooling by the mid week as the pattern switches to zonal flow.

Aviation

(12z TAFS) Issued at 415 AM PDT Sat May 9 2026

Areas of stratus and fog /IFR-MVFR/ continue to develop. The marine layer depth varies from ~ 900 feet to 2000 feet. Conditions improving to VFR today. Stratus and fog /IFR-LIFR/ redevelop tonight and Sunday morning.

Vicinity of SFO, Stratus /MVFR/ mixes out to VFR by 18z today. Stratus /IFR/ develops tonight and Sunday morning. West wind 5 to 10 knots increasing to 15 to 25 knots in the afternoon and early evening. West wind near 10 knots tonight and Sunday morning.

SFO Bridge Approach, Similar to SFO.

Monterey Bay Terminals, Stratus /IFR/ mixes out to VFR by early afternoon. Stratus /IFR/ redevelops tonight and Sunday morning. West to northwest winds 5 to 15 knots.

Marine

(today through Thursday) Issued at 407 AM PDT Sat May 9 2026

Fresh to strong northwest breezes with occasional near gale force gusts will continue through the remainder of the weekend along with building rough seas. Winds become more northerly and fresh to moderate on Sunday with rough seas beginning to gradually ease late Sunday into Monday. Gentle to moderate north to northwest breezes are expected on Tuesday and Wednesday.

Watches, Warnings, Advisories

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 AM PDT Monday for Pt Arena to Pt Reyes 0-10 nm.

Small Craft Advisory until 9 PM PDT Sunday for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

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

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