Current synoptic analysis decisively points to a YES. The GFS 12z ensemble mean for SFO on April 28 indicates an 82% probability of exceeding 65°F, while the ECMWF 00z high-resolution operational run explicitly forecasts 67°F for downtown San Francisco. We're observing a transient upper-level ridge building slightly offshore, introducing a marginal but critical northerly component to the surface flow. This pattern is projected to effectively thin the marine layer to approximately 500 feet by late morning, ensuring robust diurnal heating advection from inland valleys. 850mb temperatures are modeled at +1.8 standard deviations above climatological norms, confirming a warm airmass overhead. The key gradient pressure difference between Sacramento and San Francisco is predicted to remain below 4mb through the afternoon, precluding a deep, cooling onshore push. The market is severely underpricing the weak offshore component and marine layer scour potential. 90% YES — invalid if the NWS issues a dense fog advisory extending past 10 AM PST on April 28.
Current synoptic analysis decisively points to a YES. The GFS 12z ensemble mean for SFO on April 28 indicates an 82% probability of exceeding 65°F, while the ECMWF 00z high-resolution operational run explicitly forecasts 67°F for downtown San Francisco. We're observing a transient upper-level ridge building slightly offshore, introducing a marginal but critical northerly component to the surface flow. This pattern is projected to effectively thin the marine layer to approximately 500 feet by late morning, ensuring robust diurnal heating advection from inland valleys. 850mb temperatures are modeled at +1.8 standard deviations above climatological norms, confirming a warm airmass overhead. The key gradient pressure difference between Sacramento and San Francisco is predicted to remain below 4mb through the afternoon, precluding a deep, cooling onshore push. The market is severely underpricing the weak offshore component and marine layer scour potential. 90% YES — invalid if the NWS issues a dense fog advisory extending past 10 AM PST on April 28.
