A HEAT ADVISORY has been issued for all of northern Illinois and a portion of south-central Wisconsin beginning Noon Tuesday, lasting through 7pm.
As the skies have cleared out following the storms from Monday afternoon and evening, areas of fog will likely develop early Tuesday. Southwest winds will work to usher in an unseasonably warm and humid air mass with temperatures quickly warming into the upper 80s and low 90s during the afternoon, with dew point temperatures climbing into the mid and upper 70s. This combination of high heat and moisture will push the heat index over 100 degrees, possibly for several hours, during the afternoon and early evening. Heat stress to the body can occur rather quickly for those who spend any time outdoors Tuesday.
Along with the heat will also come the risk for strong to severe storms as all of northern Illinois and southern Wisconsin are highlighted under an enhanced risk, level 3 out of 5, for Tuesday afternoon and evening. It’s still a little unclear at this point exactly what will unfold during the day Tuesday, but a likely scenario is for thunderstorms to develop to the northwest/north of the Stateline during the day, quickly racing and south and east. During the day a cap, or lid, on the atmosphere will develop which will limit the storm development early in the afternoon. But as that cap begins to weaken the chance for severe storms will increase.
The greatest risk with these storms for Tuesday will most likely be damaging winds as the storms form into more of a cluster, or line, moving towards the Stateline. While hail and tornadoes can’t be ruled out, damaging wind gusts over 60-70 mph are possible.
The timeline for these storms appears to be roughly from 4pm/5pm through 8pm/9pm, with only isolated activity occurring Tuesday night. Make sure you remain weather aware once again Tuesday, especially later in the day. It is possible that the timing/track of these storms may change a little as we get a better handle on the overall development of the storms Tuesday morning, and if the cap does hold back any activity trying to move in from the west and north.