textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1259 PM PDT Wed Oct 7 2026

- Hot inland temperatures continue through Thursday

- Sharp cool-down this weekend

- Coastal flooding and large swell this weekend

- Light rain possible early next week

SHORT TERM

Issued at 1259 PM PDT Wed Oct 7 2026 (This evening through Thursday night)

Another hot day. Inland temperatures have already climbed into the 90s, and the hottest spots will get close to 100 degrees later this afternoon. At 500 mb a ridge is extending over the Bay Area, originating from high pressure over the Channel Islands. The 850 mb temperature is 21.5C, which is well above the 90th percentile, and near the daily max for this time of year. Winds are generally onshore, which is bringing good relief to the coast, where temperatures are in the 60s and 70s. As we've seen the last few days, there is a chance for coastal fog in the morning within a shallow marine layer.

The ridge will remain in place Thursday, although it will start to weaken through the day as a cut-off low pressure system approaches from the west. This will allow the marine layer to expand a bit. Nevertheless inland temperatures will be broadly similar Thursday, and the Heat Advisory remains in effect through the day.

LONG TERM

Issued at 1259 PM PDT Wed Oct 7 2026 (Friday through next Tuesday)

The long term forecast is quite active. I'll start with a synoptic breakdown and then list the individual hazards in greater detail. By Friday the ridge will break down as the cut-off low off the coast starts to dominate the pattern. This feature will merge with the jet stream to the north and the remnants of Hurricane Rachel to the south to form a high amplitude trough over California through the weekend.

Temperatures: The pattern change will lead to a drastic drop in temperatures. High temperatures Wed-Thu are 10-20 degrees above normal for this time of year, and will drop to 5-10 degrees below normal by Saturday. Friday is the transition with some relief before the big cool down arrives Saturday. Livermore, for example, has been dealing with 100+ degree high temperatures since last Saturday, and we have 72 degrees in the forecast for this Saturday. That's the good news.

Wind: The incoming trough will bring much lower surface pressure to California, with a central pressure likely below 1000 mb somewhere in the Central Valley this weekend. By Saturday, the gradient between this low pressure and higher pressure over the Pacific will generate strong to near gale force northwesterly winds across the coastal waters and along Pacific beaches. These winds will push inland through gaps and passes as fresh to strong west - southwest winds Saturday afternoon. We're probably not quite at wind advisory level, but bring a wind breaker if you're going to Fleet Week or anywhere near the beach.

Coastal Flooding: With warm waters driven by El Nino, we are seeing some remarkable tidal anomalies. Every tidal station in the Bay Area down to Monterey is recording a full foot of residual surge (extra water above the tide table prediction). With clear skies, light winds and high pressure, this is caused primarily by thermal expansion from the warm water. The current sea surface temperatures are in the low to mid 60s, which is around 5-7 degrees above normal for this time of year. Beyond the local SST, the regional waters are quite warm across the Eastern Pacific, especially at depth. There has been a lot of talk about the 3+ C SST anomaly from El Nino (a record), but the larger anomaly is found at depth, closer to the thermocline. In the Nino 3.4 region, the water temperature at 100 m depth is over 10-13.5C above normal. That's 18-24F. Warmer water takes up more volume through thermal expansion, and the only place that extra water can go is up. A Kelvin wave of even warmer water has reached southern California, where the SSTs are in the 70s and the tidal anomaly is roughly 1.2-1.4 feet above normal. That's heading our way, moving at about 5-10 mph up the coast. All of this extra water will make the typically innocuous Spring tide driven by a normal new moon feel more like a King Tide this weekend. The incoming winds and swell will push the tide even higher. We are expecting high tides this weekend to be somewhere from 1.2 to 1.5 feet above normal. That's enough to trigger minor coastal flooding across low-lying areas in the San Francisco Bay and southern Monterey Bay. This is just a sign of things to come this season. The extra foot of water will be here for several months, including during the real king tides in Nov, Dec, and Jan.

High Surf: In addition to the high tides, there will be large waves this weekend. This is due to a combination of long period southerly swell from Hurricane Rachel and large wind waves from the near gale force conditions over the coastal waters. The forerunners from Rachel will arrive as early as late Thursday and will build in height through the weekend. A new set of westerly swell arrives Sunday from a hurricane force extratropical storm in the central north Pacific. As the swell reaches the beaches, breaking waves of 15 feet are possible. Particularly during high tide, these wave will run much further up the beach and cause erosion. There will also be stronger currents than normal due to both the large swell and big tidal swings. Expect a Beach Hazards Statement or High Surf Advisory to be issued in the next day or two.

Rain: While the moisture from the remnants of Rachel will initially be confined to the southern California, there is a potential for some wrap around moisture to bring light rain early next week. Roughly half of the European ensemble show measurable precip at SFO Monday-Tuesday, with the ensemble mean around 0.05". None of the current simulations show anything very impactful.

The cooler weather looks like it will stick around next week, as the wind and waves calm down.

AVIATION

(00Z TAFS) Issued at 426 PM PDT Wed Oct 7 2026

A shallow marine layer is expected to return again tonight but the timing of its return along the coast is a bit uncertain. Satellite imagery shows the marine layer has receded offshore and will likely take slightly longer to return than initially anticipated. Have pushed back stratus arrival for MRY and SNS to closer to 06Z. Stratus arrival for HAF was pushed back as well but confidence is lower for HAF due to a more substantial stratus push in the vicinity of HAF on satellite (compared to clear skies near MRY and SNS). Otherwise, not anticipating stratus/fog to reach interior airports. High resolution guidance is trying to resolve fog in the vicinity of SJC overnight but confidence is low given the relatively dry overnight conditions forecast. Diurnally breezy onshore winds continue during the afternoon/evening with lighter, variable to at times offshore winds overnight.

Vicinity of SFO...VFR through the TAF period. Not anticipating stratus to reach SFO tonight given the shallow nature of the marine layer. Moderate onshore winds pick up during the late afternoon/early evening with winds around 18 knots expected before winds weaken overnight.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Fog/stratus and IFR-LIFR conditions are expected tonight but the exact timing of stratus return is slightly uncertain. Pushed the stratus arrival back closer to 06-08Z with models decently resolving the drier airmass offshore/more substantial recession of stratus offshore near the Monterey Bay. The latest guidance has stratus filling in over the bay closer to 06-08Z which contributed to pushing back the arrival time. Conditions improve by late tomorrow morning with moderate NW winds expected during the afternoon.

MARINE

(Tonight through next Monday) Issued at 426 PM PDT Wed Oct 7 2026

Gentle to moderate north breezes and moderate seas continue through Thursday. Strong to near gale force north winds will develop across the northern outer waters on Friday, spreading across the rest of the waters this weekend. Rough to very rough seas will build Friday into the weekend as a result. Long period southerly swell arrives Friday with long period westerly swell arriving Sunday, with both long period swells continuing into the early part of next week.

FIRE WEATHER

Issued at 410 AM PDT Wed Oct 7 2026

Hot and dry conditions will lead to elevated fire weather conditions across the higher terrain through Thursday. Temperatures 10 to 20 degrees above normal and poor minimum relative humidity will continue away from the compressed marine layer at the coast. The higher terrain will experience active thermal belting, little-to-no recovery with nocturnal drying across the highest peaks, and thus prolonged burn periods. Winds remain the limiting factor, with diurnal winds prevailing except for light northerly/offshore flow overnight across the higher terrain. ERC values will rise to near records during the hot and dry conditions. A pattern change Friday into the weekend will bring cooler, moister, and windier conditions.

Sarment

MTR WATCHES/WARNINGS/ADVISORIES

CA...Coastal Flood Advisory from 9 AM Friday to 3 PM PDT Tuesday for CAZ006-508-529-530.

Heat Advisory until 10 PM PDT Thursday for CAZ503-504-506-508- 510-512>518.

Coastal Flood Advisory until 4 PM PDT Wednesday for CAZ506.

PZ...None.