GFS 12z and ECMWF 00z ensemble means for YYZ on April 27 consistently print max surface temperatures exceeding the 13°C threshold. GFS EPS indicates an ensemble mean of 14.6°C with a narrow ±1.8°C interquartile range. The 850 hPa analysis reveals persistent mild advection, with geopotential heights supporting a transient weak ridge axis over the Great Lakes. While a weak shortwave clips northern Ontario, YYZ remains under a favorable diurnal heating regime with moderate mixing. Expecting surface thermal response to push slightly higher than 13°C, driven by solar insolation and a marginal southerly component to the surface flow. Sentiment: Local weather Twitter accounts are noting a mild, above-average pattern for the weekend. 88% YES — invalid if a strong cold frontal passage accelerates by 6 hours.
GFS 12z and ECMWF 00z ensemble means for YYZ on April 27 consistently print max surface temperatures exceeding the 13°C threshold. GFS EPS indicates an ensemble mean of 14.6°C with a narrow ±1.8°C interquartile range. The 850 hPa analysis reveals persistent mild advection, with geopotential heights supporting a transient weak ridge axis over the Great Lakes. While a weak shortwave clips northern Ontario, YYZ remains under a favorable diurnal heating regime with moderate mixing. Expecting surface thermal response to push slightly higher than 13°C, driven by solar insolation and a marginal southerly component to the surface flow. Sentiment: Local weather Twitter accounts are noting a mild, above-average pattern for the weekend. 88% YES — invalid if a strong cold frontal passage accelerates by 6 hours.
