Weekend features heat, humidity, thunderstorms
Especially hot summer air continues to spread eastward into the Plains, with 100° readiings spilling into the Dakotas and Nebraska. This dome of hot air continues its relentless march eastward, reaching Chicago Saturday. Some moderation from the intense Plains’ heat is expected as it mixes with the current pleasant air mass retreating eastward from Chicago. Heat and humidity linger into Sunday and even Monday, but increasing clouds help restrain temps.
In this regime, the jet stream is close enough to our north to keep the upper atmosphere unstable, and southwest winds straight from the western Gulf bring in the humidity with enough moisture for a good chance of thunderstorms Saturday and an even better chance Sunday and Monday. From Tuesday on, heat and humidity retreat southward, replaced by a strengthening Canadian high pressure cell complete with pleasant temperatures and humidity.
-Dennis Haller, WGN-TV Meteorologist