GFS 00z and ECMWF 12z ensembles are tightly clustered, indicating a persistent post-frontal airmass for Chicago on April 28th. Current operational runs for ORD project peak 2m AGL temps primarily in the 45-48°F band. Warm air advection signals are absent; a strong high-pressure ridge with northerly flow dominates. The probability density function for daytime highs shows minimal tail risk reaching 52-53°F. This range is firmly outside current model consensus. 95% NO — invalid if GFS/ECMWF shift >5°F warmer on subsequent 06z/18z runs.
GFS 00z and ECMWF 12z ensembles are tightly clustered, indicating a persistent post-frontal airmass for Chicago on April 28th. Current operational runs for ORD project peak 2m AGL temps primarily in the 45-48°F band. Warm air advection signals are absent; a strong high-pressure ridge with northerly flow dominates. The probability density function for daytime highs shows minimal tail risk reaching 52-53°F. This range is firmly outside current model consensus. 95% NO — invalid if GFS/ECMWF shift >5°F warmer on subsequent 06z/18z runs.
