GFS and ECMWF ensemble means consistently forecast a high of 60-62°F for Seattle on May 10. Persistent onshore flow and a deep marine layer, reinforced by an approaching upper-level shortwave, will provide significant advective cooling, firmly capping diurnal heating. This tight synoptic setup makes the 60-61°F band highly probable, preventing any significant upward deviation. The market is currently underpricing the stability of this precise thermal equilibrium. 85% YES — invalid if the GFS operational run shifts >2°F higher by May 8.
GFS and ECMWF ensemble means consistently forecast a high of 60-62°F for Seattle on May 10. Persistent onshore flow and a deep marine layer, reinforced by an approaching upper-level shortwave, will provide significant advective cooling, firmly capping diurnal heating. This tight synoptic setup makes the 60-61°F band highly probable, preventing any significant upward deviation. The market is currently underpricing the stability of this precise thermal equilibrium. 85% YES — invalid if the GFS operational run shifts >2°F higher by May 8.
