NWP consensus from the 00z ECMWF and GFS operational runs, alongside their respective ensemble means (GEFS, ENS), consistently indicate 850mb temperatures for KSEA on April 28 peaking at +6C, translating to surface highs around 62-65°F. While a weak upper-level ridge provides some synoptic support for above-normal conditions, persistent onshore flow from the Puget Sound Convergence Zone, evidenced by 12z WRF-ARW 10m wind fields, will initiate a robust marine push. This coastal advection will decisively moderate temperatures, preventing the sustained thermal advection required for the 68-69°F band. Historical climatology for April 28 shows 68°F as a +2.5 standard deviation anomaly, a rare occurrence not supported by current mesoscale models. Sentiment: Local forecasting models are trending slightly cooler than earlier runs. 90% NO — invalid if 500mb heights exceed 5800m over Puget Sound.
NWP consensus from the 00z ECMWF and GFS operational runs, alongside their respective ensemble means (GEFS, ENS), consistently indicate 850mb temperatures for KSEA on April 28 peaking at +6C, translating to surface highs around 62-65°F. While a weak upper-level ridge provides some synoptic support for above-normal conditions, persistent onshore flow from the Puget Sound Convergence Zone, evidenced by 12z WRF-ARW 10m wind fields, will initiate a robust marine push. This coastal advection will decisively moderate temperatures, preventing the sustained thermal advection required for the 68-69°F band. Historical climatology for April 28 shows 68°F as a +2.5 standard deviation anomaly, a rare occurrence not supported by current mesoscale models. Sentiment: Local forecasting models are trending slightly cooler than earlier runs. 90% NO — invalid if 500mb heights exceed 5800m over Puget Sound.
