Issued at 907 AM PDT Sun Aug 9 2026
The marine layer has compressed to around 800 feet in depth this morning per the OAK Upper Air Sounding. As such, will maintain current Heat Advisory across the interior through 10 PM this evening. With strong high pressure over the Desert Southwest, still expecting today to be the warmest of the next 7 days. Will need to evaluate late this morning and/or early afternoon whether or not to cancel the Heat Advisory for portions of the region.
RGass
, Issued at 1206 AM PDT Sun Aug 9 2026 (Today and tonight)
The 00Z balloon observed a 925 mb temperature of 30.35 degrees Celsius (third hottest for the date and time), 850 mb temperature of 28.75 degrees Celsius (second hottest for the date and time), and 500 mb height of 5970 meters (record for the date and time). Satellite shows stratus clearing off the coast due to a strengthening ACV-SFO surface pressure gradient. Northerly/offshore flow down the Northern Sacramento Valley Sunday morning will help push the marine layer back to the coast. Both of these factors should support Sunday being the hottest day of this event; however, if the marine layer prevails and northerly/offshore winds don't develop we could have a repeat of Saturday with our forecast being too hot for the lower elevations. Nonetheless, temperatures will be 10 to 15 degrees above normal outside of the marine layer influence with widespread moderate HeatRisk and areas of major HeatRisk in the higher terrain. Minor coastal flooding is expected during the highest high tide (evening/overnight) for bayshore locations along the San Francisco Bay, San Pablo Bay, and Monterey Bay through Thursday morning. Have opted to leave the Pacific Coast out as it would be marginal and overnight if it occurred; however, high tide may cutoff access to some beaches.
..issued at 1206 AM PDT Sun Aug 9 2026 (Monday through Saturday)
Cooling trend kicks off Monday as upper-level shortwave troughing develops off the West Coast. This will moderate temperatures to near normal, deepen the marine layer bringing a chance for drizzle, and increase onshore flow. A reinforcing trough Wednesday will bring more prominent troughing off the West Coast Thursday and into the weekend. This along with a resurgence in monsoonal moisture may be enough to bring elevated rain showers/thunderstorms to the forecast. While there's no mention in the official forecast now, it may be warranted as we get closer.
(18z TAFS) Issued at 1040 AM PDT Sun Aug 9 2026
Stratus is largely receding with the exception of HAF where an eddy will keep stratus variable through the afternoon. VFR, outside of HAF, through this evening with breezy onshore winds during the afternoon/evening. Stratus returns overnight but confidence is mixed on the exact timing. HRRR guidance suggests a patchy return late tonight while HREF guidance shows a more traditional widespread early return of stratus. It will likely be a mix of both where stratus is widespread again tonight but may return later in the night. Initial clearing times look to be between 17-18Z but it could clear as early as 16Z (persistence forecast).
Vicinity of SFO, Stratus is clearing over the SF Bay with VFR conditions expected through this evening. Stratus is forecast to return around 09-10Z and persist through late Monday morning. Highest confidence in IFR CIGs tonight. Breezy onshore winds expected during the afternoon/evening today and again tomorrow.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, VFR but some uncertainty remains as to the timing of stratus return later today. The current TAF has stratus returning between 04-06Z with IFR to LIFR ceilings expected. At the same time, an otter eddy is developing in the Monterey Bay this morning which may result in additional cloud cover pushing into MRY/SNS early this afternoon. Confidence is low that this will occur but it remains a possibility. Breezy onshore winds are expected this afternoon/evening before winds weaken overnight.
(today through Friday) Issued at 907 AM PDT Sun Aug 9 2026
Fresh to strong northwest winds persist with rough seas up to 12 feet today through mid week. Northern coastal waters will be hazardous for small craft with occasional near gale force gusts possible through early week. The San Francisco Bay north of the Bay Bridge into the Delta will have gusty onshore winds through late evening. Long period southerly swells at around 15 to 17 seconds continue.
Ca, Coastal Flood Advisory until 2 AM PDT Thursday for CAZ006-506- 508-529-530.
Heat Advisory until 10 PM PDT this evening 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 until 3 AM PDT Monday for Pt Arena to Pt Reyes 0-10 nm.
Small Craft Advisory until 9 PM PDT Monday for Pt Arena to Pt Reyes 10-60 NM.
