textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1234 PM PDT Thu May 21 2026

- Diurnally driven onshore winds during the afternoon and early evening

- Warm and dry weather through Friday leads to elevated fire weather concerns for the interior Bay Area and Central Coast

- Gradual cooling trend begins Friday with seasonal temperatures for the upcoming weekend

SHORT TERM

Issued at 1234 PM PDT Thu May 21 2026 (This evening through Friday)

Today we continue to see dry conditions across the interior and with afternoon maximum temperatures reaching the lower 80s to lower 90s under sunny skies. Meanwhile, the coast will stay cooler thanks the ~1000 ft marine layer where we are expecting the upper 50s to middle 60s. With the large scale pattern aloft is defined by a through over the northern Rocky Mountains and a building ridge over the northeastern Pacific. This pattern largely supports onshore winds at the surface with coastal breezes developing each afternoon and evening.

Tonight, expect the marine layer to remain steady, yet the inland extend is likely to increase into the coastal adjacent valleys early Friday morning. However, similar to today, these low clouds will quickly retreat to the coastline by late morning.

Friday we are expecting a slight cool down in afternoon temperatures as the trough shifts eastward allowing for a deeper marine layer to return. Coastal areas are likely to remain in the upper 50s to middle 60s with the interior warming into the upper 70s to middle 80s. The only far interior areas like Pinnacles National Park, King City, San Lucas, and San Ardo have the potential to reach 90 deg F.

LONG TERM

Issued at 1234 PM PDT Thu May 21 2026 (Friday night through next Wednesday)

The cooling trend will continue into this upcoming weekend with temperatures returning to near seasonal averages. This is as the marine layer is forecast to deepen to ~1500 ft. Cannot rule out late evening and early morning coastal drizzle during this timeframe as the boundary layer remains very moist.

By late Monday and early Tuesday, a frontal boundary is forecast to sweep across the region. This would bring the potential for drizzle and/or light rain as the front moves from north to south across the Bay Area and Central Coast. In wake of the frontal passage, the marine layer may mix out and allow for coastal locations slightly warmer compared to this weekend.

AVIATION

(18Z TAFS) Issued at 1107 AM PDT Thu May 21 2026

Clear skies across the interior with an expansive stratus deck along the coast. Kept HAF overcast throughout the day but a brief period of clearing is likely for MRY and SNS. Current thinking is that the marine layer will deepen to around 1000 ft tonight with a mix of IFR to MVFR stratus across the interior. LIFR and fog is expected directly along the coastline with fog potential increasing by early tomorrow morning. Clearing is expected by late tomorrow morning/early afternoon.

Vicinity of SFO...Winds strengthen to around 17 knots this afternoon/evening before easing overnight. Moderate confidence that MVFR CIGs will reach SFO around 10Z with some potential for CIGs to briefly drop below 1000 ft. It is worth noting that the HRRR shows a "donut hole" developing over SFO this morning stratus filters in through the Golden Gate Gap and fills into the East Bay/SF Bay but does not reach SFO. Confidence is slightly higher that a CIG will reach SFO overnight but it is worth noting their is some potential for conditions to remain VFR overnight.

SFO Bridge Approach...MVFR to IFR CIGs are likely to develop over the SF Bay overnight with clearing by late tomorrow morning.

Monterey Bay Terminals...CIGs have cleared from MRY and SNS with a brief period of VFR expected through 01/02Z. Given the expansive stratus deck just offshore, opted to push the arrival of stratus earlier in the TAF. Confidence increases in stratus returning around 01/02Z but it may return earlier if another eddy develops within the Bay. Generally expecting fog chances to increase early tomorrow morning, particularly at SNS but would not rule out patchy fog impacting MRY. Breezy onshore winds during the afternoon/evening will weaken overnight, becoming light to variable.

MARINE

(Today through Tuesday) Issued at 945 AM PDT Thu May 21 2026

Fresh to strong northerly winds continue across the far northern outer waters, resulting in hazardous conditions and rough seas through Thursday. Moderate northwesterly breezes and moderate seas will prevail for the rest of the waters. Conditions improve into the weekend as seas and northwesterly breezes become moderate with the occasional fresh to strong breeze possible across the far northern outer waters.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory until 3 AM PDT Friday for Pt Arena to Pt Reyes 10-60 NM.