textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 140 PM PDT Wed Aug 26 2026

- Temperatures near to slightly below seasonal averages persist within the shallow marine layer through Thursday

- Seasonably warm and very dry conditions continue above 1000 feet and the far interior through Thursday

- Pattern change Friday into the weekend brings cooler temperatures and increased potential for tropical moisture

SHORT TERM

Issued at 140 PM PDT Wed Aug 26 2026 (This evening through Thursday night)

Coastal stratus and fog retreated to the coast as of late morning giving way to mostly sunny skies across the interior. Meanwhile, smoke from the Timber Fire and newly developed Plaskett Fire continue to move toward the northeast as 500 MB winds are southwesterly. Today is forecast to be the warmest day of the week with temperatures topping out in the upper 80s to mid 90s across the interior and up to 107 within the warmest regions of southern Monterey County. The shallow marine layer and continued onshore winds will keep conditions cooler near the coast and across San Francisco. A gentle to moderate onshore breeze develops in the afternoon and evening hours with gusts of 20 to 35 mph at the coast, through gaps and passes, and within the favored valleys.

Tonight, much less confidence in stratus and/or fog development late in the evening and into Thursday morning as the region remains between a trough of low pressure off of the Pacific Northwest coast and high pressure over the Four Corners region.

Thursday, we are forecasting an increase in mid/upper level moisture to advect northeastward across the region from the remnants of Tropical Storm Iselle. Thus, have added a 15% probability for rain showers across the Central Coast, South Bay, and East Bay for Thursday afternoon. The probability of thunderstorms remains extremely low, but cannot be ruled out as there is some MUCAPE (instability aloft) forecast by several CAMs and deterministic models. However, cannot rule out gusty and erratic winds in and around any virga (rain not reaching the surface), sprinkles, or light rain showers that are able to develop. See the FIRE WEATHER section below for more information.

LONG TERM

Issued at 140 PM PDT Wed Aug 26 2026 (Friday through next Tuesday)

PWAT values approach 1.25" and increase to greater than 1.50" by Friday morning lending to a greater potential for wetting rains. Have extended the 15% probability for rain showers to include the Bay Area and North Bay from Friday morning through Friday afternoon. However, widespread wetting rains (greater than 0.10") is unlikely.

The approaching trough will also result in a cooling trend with temperatures dropping to below seasonal averages. The increased PWATs decrease as the aforementioned trough shifts inland by Friday night and lower to around 0.50" by Saturday night. This feature will also lead to a tightening pressure gradient which would lead to breezier winds Friday and into the weekend. Gusts are currently forecast to reach between 25 to 35 mph along the coast and through favored gaps, valleys, and passes. Zonal flow develops over the weekend holding temperatures steadily below normal.

Another reinforcing trough develops off of the Pacific Northwest coast by Monday, allowing afternoon temperatures to be some 10-20 degrees below seasonal averages. The current forecast has the potential for rain showers returning towards the middle of next week. However, this is heavily dependent on the evolution of conditions over the tropical Eastern Pacific. Thus, confidence is very low at this time.

AVIATION

(00Z TAFS) Issued at 533 PM PDT Wed Aug 26 2026

It's VFR across the forecast area except in the area of the Timber Fire smoke and haze may reduce slant range and surface visibilities. 24 hour trends are mainly warmer and drier across the forecast area and satellite imagery shows stratus and fog located mainly over the outer CA coastal waters. The ACV-SFO pressure gradient strengthened to 4.9 mb this afternoon, while the SFO-SAC pressure gradient is 2.4 mb. Coastal stratus and fog /IFR-LIFR/ redevelop tonight and Thursday morning under a compressed marine layer. Coastal stratus and fog mix out to VFR by late Thursday morning and afternoon.

Vicinity of SFO...VFR. West wind 20 to 28 knots until 04z then easing to near 10 knots tonight and Thursday morning. West wind increasing to 20 to 25 knots Thursday afternoon to mid evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR except tempo stratus and fog /IFR-LIFR/ 11z-15z Thursday morning. Mid level clouds may result in a passing high based shower Thursday afternoon.

MARINE

(Tonight through next Monday) Issued at 140 PM PDT Wed Aug 26 2026

Fresh to strong northwest winds will continue today into the weekend with moderate wind driven seas. Occasional gale force gusts in the outer and inner waters are expected through the weekend. A long period southerly swell will build late in the week becoming 17-18 seconds by Friday and persist through at least early Sunday.

FIRE WEATHER

Issued at 1209 AM PDT Wed Aug 26 2026

Not much has changed in terms of the fire weather threat, with near critical fire weather conditions persisting in the higher elevations above 1000 feet through Thursday due to warm and dry conditions. Overnight humidity recoveries remain poor to very poor within these areas and the impact of the marine layer inversion leads to temperatures warmer than the seasonal average, especially within the Santa Lucia range and the interior Central Coast where temperature are running as much as 15 to 20 degrees above the seasonal average. Model output suggests that an offshore flow has set up over the Big Sur coast at the 925 mb level, supporting the risk for overnight nocturnal drying in the interior Central Coast and particularly surrounding the Timber Fire. Last night I had noted that the southwest winds seemed to bring in more moist air into the Santa Lucia range, and that the overnight diminishing of winds when combined with the offshore push led to an unusual situation where the maximum daily relative humidities took place during the day. This remains the case, up until the ridgeline parallel to the Big Sur coast when the southwest winds begin to downslope and dry the region. Unfortunately there aren't a lot of weather station in these areas to verify the conceptual model. Smoke transport from the Timber Fire will continue to peak in the afternoon and evening with the plume spreading towards the Salinas area. Friday into the weekend, a pattern change should allow for some relief as an upper level trough comes into the region bringing cooler temperatures and a deeper marine layer.

DialH

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory until 9 AM PDT Friday 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.