ECMWF and GFS ensemble means consistently project Toronto's maximum temperature on April 28th to struggle clearing 9°C. A deep upper-level trough is anchoring persistent cold air advection across the Great Lakes, well suppressing the 12.5°C climatological normal for this date. This strong negative anomaly provides a clear signal. 95% YES — invalid if current GFS 12z run deviates by >2°C on its 00z output.
ECMWF and GFS ensemble means consistently project Toronto's maximum temperature on April 28th to struggle clearing 9°C. A deep upper-level trough is anchoring persistent cold air advection across the Great Lakes, well suppressing the 12.5°C climatological normal for this date. This strong negative anomaly provides a clear signal. 95% YES — invalid if current GFS 12z run deviates by >2°C on its 00z output.
