GFS and ECMWF ensemble means are consistently signaling a high of 54-55°F for Chicago on April 27, with the 75th percentile only reaching 58°F. A lingering northerly boundary layer flow off Lake Michigan will suppress diurnal warming, preventing the precise 56-57°F band. Thermal advection profiles indicate insufficient uptick. The probability mass distribution is firmly centered below this narrow window. 90% NO — invalid if the 12Z NAM model shifts to a sustained south-southwesterly flow.
GFS and ECMWF ensemble means are consistently signaling a high of 54-55°F for Chicago on April 27, with the 75th percentile only reaching 58°F. A lingering northerly boundary layer flow off Lake Michigan will suppress diurnal warming, preventing the precise 56-57°F band. Thermal advection profiles indicate insufficient uptick. The probability mass distribution is firmly centered below this narrow window. 90% NO — invalid if the 12Z NAM model shifts to a sustained south-southwesterly flow.
