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

UPDATE

Issued at 643 PM PDT Thu May 21 2026

Stratus continues to impact the immediate coast with some inland expansion across the Monterey Bay region, and a finger of stratus coming through the Golden Gate into the Berkeley area. The Bodega Bay profiler is reporting a marine layer depth of around 1000 to 1500 ft, which is conducive to expanded stratus development into the inland valleys through the early hours of Friday morning.

DialH

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 extent 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

(00Z TAFS) Issued at 445 PM PDT Thu May 21 2026

Currently a mixed bag of LIFR-VFR at the terminals. Moderate to high confidence on IFR-LIFR conditions returning to all terminals with the exception of the interior terminals of LVK and SJC. Uncertainty lies in the depth of the marine layer. Currently shallow at around 500 feet, it is expected to deepen to 1,000 feet tonight with an approaching surface trough. This would typically lift ceilings; however, the moist southwesterly flow ahead of it may lead to fog formation with the coastal terminals at greatest risk. Diurnal winds will prevail.

Vicinity of SFO...Currently VFR with northwesterly flow. Moderate confidence (40%) on a sub-VFR ceiling developing at the terminal, likely on the cusp of IFR/MVFR. Diurnal winds will prevail.

SFO Bridge Approach...Low clouds are expected to begin impacting the San Mateo Bridge Approach tonight as early as 04Z. As they come through the Golden Gate Gap, they will make contact with the East Bay Hills and then spread north and south; thus, low cloud probabilities are higher for the East Bay and OAK with only moderate confidence (45%) between SJC and SFO.

Monterey Bay Terminals...Currently VFR with westerly flow at MRY and MVFR with northwesterly flow and haze at SNS. High confidence on LIFR conditions returning to both terminals tonight with fog possible. VFR is expected by late morning with IFR stratus sticking close to the coast during the day.

MARINE

(Tonight through next Tuesday) Issued at 445 PM PDT Thu May 21 2026

Fresh to strong northerly winds and moderate seas continue across the far northern outer waters through early Friday morning. Winds diminish to moderate to fresh with occasional strong gusts Friday into Saturday. Elsewhere, a moderate breeze and moderate seas continue into the weekend. Conditions further improve Sunday into early next week with a gentle to moderate breeze expected over the coastal waters. Unsettled weather returns mid to late week with strengthening winds and building seas.

MTR WATCHES/WARNINGS/ADVISORIES

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