Severe weather could threaten the Chicago area later this week.
The transition to a cooler pattern may get underway with an atmospheric bang Wednesday night. While a few scattered and isolated, low coverage thunderstorms are possible during the day Wednesday, it’s Wednesday night when a more significant severe weather threat appears to be taking shape.
While many details remain to be firmed up, it seems the period from midnight Wednesday to 4 a.m. Thursday appears to be the current focus of concern. That’s when a fast moving squall line could sweep out of Wisconsin into Northern Illinois and Northwest Indiana.
A classic “northwest flow” situation is taking shape. That’s an atmospheric setting which threatens several bowed lines of severe thunderstorms with even the potential for a derecho, a fast, moving damaging line of thunderstorms. It is set to race southeastward beneath a powerful northwesterly jet stream and infuses the fast moving storms with wind energy that can produce an extended path of damage.