The climatological probability of a 37°F maximum temperature in Chicago on April 29 is exceedingly low. Mean daily highs for this period are consistently in the low-50s°F. Achieving a sub-38°F high would necessitate an extreme Arctic air advection event coupled with a pronounced synoptic deep troughing pattern, conditions that are not registering as high-probability outcomes in current GFS/ECMWF ensemble means or deterministic runs. This is a significant negative temperature anomaly far outside the 2-sigma range. 98% NO — invalid if 00Z/12Z GFS/ECMWF deterministic runs within 72h project a >70% likelihood of 37F or below.
The climatological probability of a 37°F maximum temperature in Chicago on April 29 is exceedingly low. Mean daily highs for this period are consistently in the low-50s°F. Achieving a sub-38°F high would necessitate an extreme Arctic air advection event coupled with a pronounced synoptic deep troughing pattern, conditions that are not registering as high-probability outcomes in current GFS/ECMWF ensemble means or deterministic runs. This is a significant negative temperature anomaly far outside the 2-sigma range. 98% NO — invalid if 00Z/12Z GFS/ECMWF deterministic runs within 72h project a >70% likelihood of 37F or below.
