Market mispricing the thermal inertia for late April. KSEA climatological mean high for April 28 is 58.7°F (1991-2020 normals). A high of 51°F or below demands a robust, anomalous synoptic pattern: persistent deep troughing, significant cold air advection from the Gulf of Alaska, and a tenacious stratiform cloud deck limiting insolation. While the Puget Sound Convergence Zone can locally suppress temps, the regional high will likely exceed this threshold. Probabilistic output from long-range ensemble guidance typically shows higher confidence in values closer to or above the climatological mean for this date, with a sub-25% historical frequency for a max temp <= 51°F. Betting on the strong pull of climatology against a significant negative temperature anomaly without clear model support. 85% NO — invalid if GFS/ECMWF operational runs converge on a -2 sigma cold anomaly by D-5.
Market mispricing the thermal inertia for late April. KSEA climatological mean high for April 28 is 58.7°F (1991-2020 normals). A high of 51°F or below demands a robust, anomalous synoptic pattern: persistent deep troughing, significant cold air advection from the Gulf of Alaska, and a tenacious stratiform cloud deck limiting insolation. While the Puget Sound Convergence Zone can locally suppress temps, the regional high will likely exceed this threshold. Probabilistic output from long-range ensemble guidance typically shows higher confidence in values closer to or above the climatological mean for this date, with a sub-25% historical frequency for a max temp <= 51°F. Betting on the strong pull of climatology against a significant negative temperature anomaly without clear model support. 85% NO — invalid if GFS/ECMWF operational runs converge on a -2 sigma cold anomaly by D-5.
