textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1201 AM PDT Thu Aug 27 2026

- Slight chance of thunderstorms this morning, with shower chances through Friday

- Slight cooling today, with temperatures close to seasonal averages

- Cooling trend continues Friday into the next week

UPDATE

Issued at 725 AM PDT Thu Aug 27 2026

Have updated the forecast to include a slight chance of thunderstorms through 10 AM this morning for the Central Coast. This is as we are seeing thunderstorms offshore and moving into Santa Barbara and San Luis Obispo counties. While there still appears to be limited instability across the Central Coast, we have added them due to the convection offshore. We will continue to monitor this closely throughout the day.

RGass

SHORT TERM

Issued at 1201 AM PDT Thu Aug 27 2026 (Today and tonight)

Stratus clouds are developing at the immediate coast and are expected to generally remain confined to the coastal valleys overnight before mixing out through Thursday morning. Zooming out into the Pacific reveals some interesting activity off the coast as some storm cells with frequent lightning have developed around a moisture gradient. The latest forecast update includes a slight chance for thunderstorms for the morning hours, around the time that these cells would impact the coast if they hold together. As of the time of writing, they have been dissipating as they move towards our coastal waters, but the night shift will continue monitoring these cells as they approach and issue any forecast updates and products as they become necessary. Beyond the morning hours, tropical moisture sourced from the remnants of Tropical Storm Iselle will come into the state, and slight chances for showers persist through the day. Low, but non-zero, chances for thunderstorms will tick up again in the afternoon and evening hours, but the limiting factor appears to be insufficient atmospheric instability. Will continue to monitor the situation as it evolves through the day.

The large-scale weather pattern remains dominated by the balance between the ridging over the Desert Southwest and the troughing over the eastern Pacific. The ridging has generally won out over the last few days, but today will mark the very beginnings of a transition to a more troughing-dominated pattern. Temperatures will remain near to slightly above the seasonal averages, but we will see a slight cooldown as highs reach the upper 80s to middle 90s inland, the upper 90s to the triple digits in the warmest interior locations, the lower 70s to the lower 80s near the Bays, and the lower to middle 60s at the Pacific coast. Breezy onshore winds will develop in the afternoon and evening hours with gusts of 20 to 30 mph at the coasts.

For a discussion of weather-related impacts to the fire weather situation, see the FIRE WEATHER section.

LONG TERM

Issued at 1201 AM PDT Thu Aug 27 2026 (Friday through Wednesday)

The progression of the trough, and with it the cooling trend and associated tropical moisture, continue into Friday with the slight chances for showers continuing through the day. Later on Friday into the weekend, the tropical moisture dips to the south but the deepening trough remains, and cooler temperatures continue into the middle of next week. Temperatures reach their coolest on Monday, around 5 to 15 degrees below seasonal averages, as high reach the 70s throughout the inland valleys, the 80s along the warmest interior Central Coast regions, and the upper 50s to the 60s at the Bays and the Pacific coast. The trough will start to flatten out, but remains in place with temperatures slow to rise. The forecast shows rain chances returning to the region for the middle of next week, but this is critically dependent on how conditions evolve in the tropical Eastern Pacific, so confidence remains low.

AVIATION

(12Z TAFS) Issued at 428 AM PDT Thu Aug 27 2026

VFR prevails with the exception of KHAF. The marine layer has remained around 1000ft, unorganized and made little to no inland push through the overnight hours. VFR is expected to prevail for most terminals through the forecast period. Confidence is low on the potential for IFR/LIFR ceilings developing late in the forecast period along the coastal sites, especially KMRY and KSNS.

Vicinity of SFO...The marine layer has remained at the coastline overnight. A fetch of offshore flow just above the marine layer will help maintain VFR conditions now through late tonight into early Friday morning. Will have to see how well the marine layer recovers once flow in the lower boundary layer returns to onshore late in the forecast period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR with a slight chance of LIFR ceilings until mid-morning. Offshore flow this far south is more pronounced and expected to help maintain VFR conditions through the forecast period. There is a slight chance of showers developing offshore and moving through the Central Coast and Monterey Bay terminals through the forecast period. Elevated thunderstorms are not currently in the forecast, and chances remain low, but cannot be ruled out entirely.

MARINE

(Today through Tuesday) Issued at 428 AM PDT Thu Aug 27 2026

Fresh to strong northwest winds will persist today and continue into the weekend with moderate wind driven seas. Near gale force gusts are possible over the northern outer and coastal waters this afternoon into tonight. A long period southerly swell will begin to build above 16 seconds Friday morning, peaking around 17-18 seconds by Saturday morning, and gradually decline Sunday into Monday.

FIRE WEATHER

Issued at 1201 AM PDT Thu Aug 27 2026

One more day of near-critical fire weather conditions above 1000 feet, especially across the Central Coast, as warm and dry conditions continue above the marine layer inversion and overnight humidity recoveries remain poor. One thing to note is that even with the slight chance of rain today into Friday, we are not expecting wetting rains to develop, while a small but non- zero chance for thunderstorms raises the specter for a dry lightning- induced fire start in the higher elevations. Across the Timber and Plaskett Fires, light offshore winds overnight may lead to nocturnal drying concerns at the higher elevations. A pattern change Friday into the weekend will bring cooler temperatures and likely a deeper marine layer, bringing progressively more relief to some of the higher elevations.

DialH

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory until 9 AM PDT Saturday for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.