textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 104 PM PDT Sat Aug 8 2026

- Warm to hot conditions will result in moderate to major HeatRisk for the interior through Sunday

- Near-critical fire weather conditions in the higher terrain through Sunday

- Minor coastal flooding for bayshore locations along the San Francisco, San Pablo, and Monterey bays through Thursday morning

SHORT TERM

Issued at 104 PM PDT Sat Aug 8 2026 (This evening through Sunday night)

The deeper marine layer, around 1600 feet in depth per the OAK Upper Air Sounding, early this morning has resulted in slightly cooler temperatures across the lower elevations. As high pressure over the Four Corners region continues to build westward across the Bay Area and Central Coast, temperatures aloft remain very warm to hot! As such, the Heat Advisory remains in effect for much of the interior through 10 PM PDT Sunday. This is as the marine layer is forecast to eventually compress to around 500 feet by Sunday morning under the building high pressure and 850mb temperatures are between 27-30C Sunday afternoon. Afternoon temperatures in the Heat Advisory are forecast to warm into the mid 90s and up to 105 deg F in the warmest interior locations where the most widespread moderate to isolated major HeatRisk are present. Overnight lows are also forecast to be warm and range from the mid 60s in the hills just above the marine influences to low 80s (especially in the higher elevations). Afternoon temperatures closer to the coast are forecast to be in the 60s to mid 70s largely due to the onshore winds and marine influences. Overnight lows near the coast are forecast to be in the 50s as stratus returns overnight. If the depth of the marine layer is higher than currently forecast, temperatures will be slower to warm Sunday afternoon.

Minor coastal flooding is also expected around the time of the highest high tide (evening/overnight) for bayshore locations along the San Francisco, San Pablo, and Monterey bays through Thursday morning. The Pacific Coast may need to be added Sunday through Tuesday to the advisory. We are waiting to see how high the observed levels are tonight (Saturday) before making that decision. Please see the CFW product we have out for additional details. Also, for more on the fire weather concerns this weekend, please see the Fire Weather Section of the AFD below.

During this weekend's heat event, remember:

* Stay hydrated and drink plenty of fluids. * Wear lightweight and light-colored clothing. * Reduce time spent outdoors or stay in the shade. * Never leave people or pets unattended in vehicles. * Use sunscreen if going to the coast or the pool.

LONG TERM

Issued at 104 PM PDT Sat Aug 8 2026 (Monday through next Friday)

Ensemble clusters are in decent agreement that a mid/upper level shortwave trough will develop by Monday off of the West Coast. However, the high pressure aloft will persist over the Four Corners region and over the eastern Pacific. This will bring temperatures closer to near seasonal norms by Monday and through Wednesday, also lowering HeatRisk to the minor category across the interior.

By late in the week, temperatures cool to below normal as a mid/upper level through develops off of the Bay Area and Central Coast. As this low pressure approaches the coastline late in the week and monsoonal moisture advects northward around the high over the Four Corners, there is the potential for high-based convection. The main question is if there will be enough instability. While this is still far out in time and low confidence, any dry lightning would be problematic from a fire weather standpoint. Be sure to check back for additional details as we move closer to midweek.

AVIATION

(18Z TAFS) Issued at 1135 AM PDT Sat Aug 8 2026

Tricky forecast this TAF period. The marine layer overperformed this morning at a depth of 1600 feet. Majority of model guidance kept signaling a compression below 1000 feet, but considering the recent observations and expected onshore wind support, it will likely be closer to 1200-1500 feet tonight. That being said, a mixed bag of borderline IFR-LIFR ceilings are expected after 02Z Sunday for coastal sites and after 04Z Sunday for inland sites. SJC is the only inland site that will see low-end MVFR ceilings this TAF period. Low confidence on whether LVK will develop a brief MVFR-IFR ceiling as it is dependent on how far inland the marine stratus travels. If a ceiling does develop, it will likely be sometime after 10Z Sunday. Overall, medium confidence on stratus arrival for Bay Area sites. Aside from stratus, typical diurnal onshore wind pattern prevails through the TAF period with most sites shifting to VFR by the early afternoon.

Vicinity of SFO...VFR with northwest winds increasing to 12-18 kt this afternoon and ease to 7-10 kt overnight. Marine stratus returns again tonight with IFR ceilings. In terms of timing, relied on persistence for SFO but expect a delayed arrival for OAK (~04Z Sunday). Medium confidence on exactly when they will arrive, though ceilings are expected to persist until 17-18Z tomorrow.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus has receded to the coastline where the otter eddy resides. VFR through the afternoon with high confidence for IFR ceilings to roll in around 02-03Z this evening. Overnight, ceilings may drop to LIFR (OVC003-004) though there is low confidence on when and how long those conditions will last.

MARINE

(Today through Thursday) Issued at 918 AM PDT Sat Aug 8 2026

Fresh to strong northwest winds continue through the weekend into the work week with building rough seas up to 12 feet across the outer coastal waters. The northern coastal waters particularly will remain hazardous to small craft with occasional near gale force gusts through the middle of next week. Gusty onshore winds are forecast through Sunday across the San Francisco Bay north of the Bay Bridge to the Delta. A long period southerly swell of 15 to 17 seconds prevails through the weekend.

FIRE WEATHER

Issued at 1206 AM PDT Sat Aug 8 2026

Near-critical fire weather conditions persist through the weekend across the interior due to very hot and dry conditions. Strong thermal belting, extended burn periods, elevated PIG, and near or record BI/ERC values are expected. Temperatures will be 10 to 15 degrees above normal with a compressed marine layer. Poor minimum daytime relative humidity as low as 10% in the afternoons with little-to-no recovery overnight is expected with nocturnal drying in the highest terrain. Even with critically dry conditions, wind is the limiting factor preventing this from being a Fire Weather Watch/Red Flag Warning event. Outside of the diurnal sea breeze that will bring breezy conditions in the afternoons and evenings through gaps and passes, onshore flow will be light. Additionally, critical conditions are not expected to meet coverage or duration requirements to warrant a product. Elevated fire weather conditions are expected into next week as onshore flow increases on the heels of the near-critical hot and dry event this weekend. The upper-level pattern along with a resurgence in monsoonal moisture may be enough to bring elevated rain showers/thunderstorms to the forecast as early as Thursday and into next weekend.

Sarment

MTR WATCHES/WARNINGS/ADVISORIES

CA...Coastal Flood Advisory until 2 AM PDT Thursday for CAZ006-506- 508-529-530.

Heat Advisory until 10 PM PDT Sunday for CAZ503-504-510-512>518.

PZ...Small Craft Advisory until 9 PM PDT this evening for SF Bay N of Bay Bridge.

Small Craft Advisory from 9 AM to 9 PM PDT Sunday for Pt Arena to Pt Reyes 0-10 nm-SF Bay N of Bay Bridge.

Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt Reyes 10-60 NM.