GFS projects a 42°F high for CHI on May 10. Arctic advection from a persistent northerly flow establishes a cold synoptic pattern. Sub-45°F is a lock. 95% YES — invalid if ridge builds quickly.
GFS projects a 42°F high for CHI on May 10. Arctic advection from a persistent northerly flow establishes a cold synoptic pattern. Sub-45°F is a lock. 95% YES — invalid if ridge builds quickly.