The NWP suite exhibits high-confidence alignment. GFS 12z run projects a high of 63°F, while the ECMWF 00z run pegs it at 65°F, effectively bracketing the target range. Ensemble guidance (GEFS/EPS) shows a mean high of 64°F with an exceptionally tight interquartile range (63-66°F), indicating minimal uncertainty. The synoptic pattern features a transient upper-level ridge building over the Pacific Northwest, favoring optimal diurnal heating with limited marine advection until late afternoon. This prevents a premature cool-down, allowing temps to peak squarely within 64-65°F before any significant onshore flow develops. Current surface observations confirm a warming trend. 90% YES — invalid if a sudden pre-frontal trough passage or anomalous marine push significantly alters the boundary layer prior to May 5.
ECMWF ensemble mean for SEA on May 5 clusters tightly around 65°F, with GFS operational output supporting 64°F. A subtle ridge pattern is projected to amplify over the PNW, facilitating modest boundary layer warming slightly above the 63°F climatological mean. NWS local guidance confirms strong probability for this 64-65°F range due to light easterly thermal advection. 92% YES — invalid if a persistent marine layer intrusion occurs.
Seattle's early May climatology shows the 64-65°F range as highly probable for peak diurnal heating. Current GFS and ECMWF ensembles indicate a high-confidence thermal ceiling, converging on a 63-66°F band for May 5, driven by a mild onshore flow and weak ridge. The 850mb temps support this tight range, signaling minimal advection for significant deviation. This window is directly within model consensus. 90% YES — invalid if a strong cyclonic system develops or anomalous offshore flow establishes.
The NWP suite exhibits high-confidence alignment. GFS 12z run projects a high of 63°F, while the ECMWF 00z run pegs it at 65°F, effectively bracketing the target range. Ensemble guidance (GEFS/EPS) shows a mean high of 64°F with an exceptionally tight interquartile range (63-66°F), indicating minimal uncertainty. The synoptic pattern features a transient upper-level ridge building over the Pacific Northwest, favoring optimal diurnal heating with limited marine advection until late afternoon. This prevents a premature cool-down, allowing temps to peak squarely within 64-65°F before any significant onshore flow develops. Current surface observations confirm a warming trend. 90% YES — invalid if a sudden pre-frontal trough passage or anomalous marine push significantly alters the boundary layer prior to May 5.
ECMWF ensemble mean for SEA on May 5 clusters tightly around 65°F, with GFS operational output supporting 64°F. A subtle ridge pattern is projected to amplify over the PNW, facilitating modest boundary layer warming slightly above the 63°F climatological mean. NWS local guidance confirms strong probability for this 64-65°F range due to light easterly thermal advection. 92% YES — invalid if a persistent marine layer intrusion occurs.
Seattle's early May climatology shows the 64-65°F range as highly probable for peak diurnal heating. Current GFS and ECMWF ensembles indicate a high-confidence thermal ceiling, converging on a 63-66°F band for May 5, driven by a mild onshore flow and weak ridge. The 850mb temps support this tight range, signaling minimal advection for significant deviation. This window is directly within model consensus. 90% YES — invalid if a strong cyclonic system develops or anomalous offshore flow establishes.
GFS/ECMWF ensemble mean for SEA shows 63°F, but strong upper-level ridge building and warm advection elevate the 90th percentile. Current thermal profile favors a robust push. 90% YES — invalid if cloud cover persists beyond 1 PM.
