Signal indicates a strong NO. Climatological averages for KSEA on May 10th pinpoint mean daily highs around 64°F (17.8°C), supported by 30-year NWS data. Current GEFS and ECMWF ensemble means for that date consistently project surface temperatures in the low to mid-60s Fahrenheit, with a tight clustering around 63-66°F, placing the 58-59°F range significantly outside the core probability distribution – approximately 1.5 to 2 standard deviations below the ensemble mean. Upper-air analysis (850mb temps) also shows insufficient cold air advection to support sustained surface highs below 60°F, even with a strong marine push. While a persistent stratus deck could limit diurnal warming, the overall synoptic pattern does not support such a pronounced cool anomaly. The probability of the high failing to reach 60°F is low. 90% NO — invalid if KSEA registers a surface high exceeding 59.5°F.
GFS and ECMWF ensemble means for Seattle on May 10 consistently project surface temps within the 57-60°F window. Persistent onshore flow and a resilient marine layer, reinforced by a weak offshore trough, will suppress significant diurnal warming. 850mb temps are benign at +3°C, preventing strong adiabatic effects. This synoptic pattern points directly to the lower end of spring temps, making 58-59°F a high-probability outcome. 90% YES — invalid if early morning stratus burns off unexpectedly quickly.
Signal indicates a strong NO. Climatological averages for KSEA on May 10th pinpoint mean daily highs around 64°F (17.8°C), supported by 30-year NWS data. Current GEFS and ECMWF ensemble means for that date consistently project surface temperatures in the low to mid-60s Fahrenheit, with a tight clustering around 63-66°F, placing the 58-59°F range significantly outside the core probability distribution – approximately 1.5 to 2 standard deviations below the ensemble mean. Upper-air analysis (850mb temps) also shows insufficient cold air advection to support sustained surface highs below 60°F, even with a strong marine push. While a persistent stratus deck could limit diurnal warming, the overall synoptic pattern does not support such a pronounced cool anomaly. The probability of the high failing to reach 60°F is low. 90% NO — invalid if KSEA registers a surface high exceeding 59.5°F.
GFS and ECMWF ensemble means for Seattle on May 10 consistently project surface temps within the 57-60°F window. Persistent onshore flow and a resilient marine layer, reinforced by a weak offshore trough, will suppress significant diurnal warming. 850mb temps are benign at +3°C, preventing strong adiabatic effects. This synoptic pattern points directly to the lower end of spring temps, making 58-59°F a high-probability outcome. 90% YES — invalid if early morning stratus burns off unexpectedly quickly.
