Seattle's early May climatological norm hovers around 65°F. Achieving 76-77°F requires robust upper-level ridging and persistent dry easterly flow, a synoptic pattern consistently absent from current long-range ensemble guidance. The strong marine layer and prevailing onshore flow typically preclude such an extreme temperature anomaly this early in the season. Historical data shows this range is a significant outlier for the date. 95% NO — invalid if GFS/ECMWF shift to strong 500mb geopotential height anomaly > +2.5σ for PACNW by May 2.
Seattle's early May climatological norm hovers around 65°F. Achieving 76-77°F requires robust upper-level ridging and persistent dry easterly flow, a synoptic pattern consistently absent from current long-range ensemble guidance. The strong marine layer and prevailing onshore flow typically preclude such an extreme temperature anomaly this early in the season. Historical data shows this range is a significant outlier for the date. 95% NO — invalid if GFS/ECMWF shift to strong 500mb geopotential height anomaly > +2.5σ for PACNW by May 2.
