Current GFS ensemble mean forecasts for May 11 consistently place Chicago highs in the 61-64°F range. While a historical thermal surge has pushed temperatures above 66°F in ~35% of recent May 11ths, the synoptic pattern lacks robust warm advection. The 500mb ridge axis is projected to remain west, keeping the region in a cooler flow. High confidence in this ceiling. 90% NO — invalid if a significant mid-week pattern shift brings an anomalous southwesterly flow.
Current GFS ensemble mean forecasts for May 11 consistently place Chicago highs in the 61-64°F range. While a historical thermal surge has pushed temperatures above 66°F in ~35% of recent May 11ths, the synoptic pattern lacks robust warm advection. The 500mb ridge axis is projected to remain west, keeping the region in a cooler flow. High confidence in this ceiling. 90% NO — invalid if a significant mid-week pattern shift brings an anomalous southwesterly flow.
