Current GFS and ECMWF operational runs, corroborated by ensemble means, project a dominant cold air mass advection for May 6 over Toronto. A potent upper-level trough will sustain northerly flow, keeping 850mb temperatures suppressed to -6°C to -9°C. This dynamic ensures minimal diurnal warming within the surface boundary layer despite potential insolation. Expect max surface temps to struggle significantly against this thermal gradient, firmly holding below 9°C. 95% YES — invalid if upper-level ridging develops by May 4.
ECMWF ensembles project a -2.5 sigma negative geopotential height anomaly, driving persistent cold advection. GFS concurs, indicating May 6 highs struggling to breach 7°C. Strong downside temp bias. 95% YES — invalid if synoptic pattern shifts north.
Current GFS and ECMWF operational runs, corroborated by ensemble means, project a dominant cold air mass advection for May 6 over Toronto. A potent upper-level trough will sustain northerly flow, keeping 850mb temperatures suppressed to -6°C to -9°C. This dynamic ensures minimal diurnal warming within the surface boundary layer despite potential insolation. Expect max surface temps to struggle significantly against this thermal gradient, firmly holding below 9°C. 95% YES — invalid if upper-level ridging develops by May 4.
ECMWF ensembles project a -2.5 sigma negative geopotential height anomaly, driving persistent cold advection. GFS concurs, indicating May 6 highs struggling to breach 7°C. Strong downside temp bias. 95% YES — invalid if synoptic pattern shifts north.
