textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1201 AM PDT Tue Sep 22 2026

- Warming trend begins today through Thursday

- Cooler conditions Friday into the weekend

SHORT TERM

Issued at 1201 AM PDT Tue Sep 22 2026 (Today and tonight)

Extensive stratus has flowed into the North Bay valleys, Monterey Bay region, Salinas Valley, Hollister area, and the East Bay west of the Berkeley Hills. Across the rest of the SF Bay Area, patches of stratus have developed near Livermore and north of San Jose, with further expansion expected through the pre-dawn hours. The cloud deck retreats back to the immediate coast late this morning into the early afternoon, but by the time it develops again tonight, the marine layer will be compressed, leading to uncertainty over just how far inland the clouds will go.

The cut-off low that gave us the last couple days of cooler temperatures is moving across the state with the center crawling through the Mojave Desert into the Great Basin. This allows for more zonal flow to come into the state and a warming trend to begin today, with high temperatures in the upper 70s to the middle 80s across the inland valleys, into the upper 80s in the far interior regions of the North Bay and southern Monterey County, the middle 60s to the middle 70s close to the Bays, and the lower to middle 60s along the immediate coast. A breezy onshore wind will develop in the afternoon and evening hours, with the strongest gusts of 20 to 30 miles per hour along the coast, through favored gaps and passes, and within the northern Salinas Valley.

As a quick side note, today will mark the autumnal equinox and the start of astronomical fall. At 505 PM Pacific time, the sun's apparent path on the Earth crosses the equator, giving us 12 hours each of sunlight and nighttime.

LONG TERM

Issued at 1201 AM PDT Tue Sep 22 2026 (Wednesday through Monday)

Slight ridging will develop over California over the next couple of days, and while the ridge axis quickly moves into the Intermountain West, the ridge influence will allow for further warming Wednesday and Thursday. High temperatures warm into the middle 80s to the middle 90s in the inland valleys, the middle 70s to the middle 80s close to the Bays, and the middle 60s to the lower 70s along the Pacific Coast. Pockets of Moderate HeatRisk are scattered across the interior regions, particularly near San Jose, the interior East Bay, and the Santa Lucia range. These pockets are not expansive enough to merit a Heat Advisory.

By Friday, a developing trough in the eastern Pacific comes into the West Coast, and a cooling trend will cause temperatures to dip near and below seasonal averages. Weekend highs range from the middle 70s to the middle 80s in the inland valleys and the middle 60s to the middle 70s close to the Bays. Temperatures will recover early next week as the trough flattens and ensemble model cluster analysis hints at a ridge developing somewhere within the western United States, although the exact impacts are not certain at this point.

AVIATION

(06Z TAFS) Issued at 1021 PM PDT Mon Sep 21 2026

Extensive MVFR-IFR stratus has flowed into the North Bay and the Monterey Bay region, and continues to develop in the SF Bay region. A deep marine layer should allow many of the inland valleys to see ceilings overnight before the stratus retreats back to the immediate coast late Tuesday morning. Low to moderate confidence in temporary scatterings at HAF and MRY around the 19-22Z timeframe. Gentle to moderate onshore winds will develop Tuesday afternoon and evening. Stratus forecasts for Tuesday night into Wednesday morning are lower confidence, particularly away from the immediate coast, as a compressing marine layer should keep stratus away from many inland regions but lower ceilings and visibilities where it does form.

Vicinity of SFO... A tricky forecast for the next several hours as the stratus feed through the Golden Gate gets deflected to the north, leaving the terminal area VFR. High resolution model output has the terminal getting MVFR ceilings imminently, but the models have not captured the current situation well and have kept the terminal VFR for the time being. If stratus forms over SFO expect the clouds to scatter out late Tuesday morning, with a moderate west breeze developing in the afternoon and evening hours. Low confidence of stratus returning Tuesday night, which most of the high resolution guidance has backed away from and may be impacted by a compressing marine layer.

SFO Bridge Approach... MVFR stratus may arrive before or after it gets to the terminal tonight, depending on how exactly the stratus develops with SF Bay. Otherwise similar to SFO.

Monterey Bay Terminals... MVFR ceilings at present with IFR conditions expected later tonight. Stratus will scatter out Tuesday late morning to the early afternoon, with moderate confidence in a brief scattering period at MRY near 19-22Z. Stratus is expected to return to MRY late in the afternoon and persist into the evening. At SNS, confidence is lower as the compressing marine layer may keep the deck away, but on the flip side, the compression could also lower ceilings and visibilities at MRY on Tuesday night.

MARINE

(Tonight through next Sunday) Issued at 826 PM PDT Mon Sep 21 2026

Moderate to fresh northwest breezes persist overnight with locally stronger winds north of Point Reyes. By Tuesday afternoon, widespread strong northwest winds prevail across the coastal waters, allowing for seas to build from moderate to rough. Northwest winds and seas remain elevated through the week with a brief period of improved conditions Wednesday night into Thursday. By Friday, winds increase with building rough seas.

FIRE WEATHER

Issued at 423 AM PDT Mon Sep 21 2026

An upper-level low will support near to slightly below normal temperatures, increased diurnal winds, a deep (2,500') marine layer. Warming and drying trend kicks off Tuesday with temperatures up to 10 degrees above normal and areas of moderate HeatRisk Wednesday and Thursday. The marine layer will compress below 1,000 feet during this warm-up with nocturnal drying expected above it.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory until 5 AM PDT Wednesday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for Pigeon Pt to Pt Pinos 0-10 nm.

Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Wednesday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

Small Craft Advisory from 3 PM this afternoon to 5 AM PDT Wednesday for Pigeon Pt to Pt Pinos 10-60 NM.