A late summer heat wave is expected over the Southeast as a strong ridge of high pressure builds for the upcoming week. This will push the jet stream northward over much of the middle of the country, bringing temperatures into the mid and possibly upper 80s for northern Illinois and southern Wisconsin.
Even though temperatures weren’t that warm Sunday – officially we only reached 65 degrees, 13 degrees below average – highs Monday will climb into the mid 70s as winds shift around to the southeast. The leading edge of warm air, however, will bring the chance for morning thunderstorms Monday. These are expected to develop southwest of Rockford around sunrise, lifting northeast through the morning. Most of the activity should be done by Noon leaving skies partly cloudy during the afternoon. You’ll also notice the humidity increase as dew point temperatures rise back into the mid 60s Monday evening, and then low 70s Tuesday, Wednesday and Thursday. This will likely push the heat index back into the low 90s for some.
The high pressure system centered over the southeast will help bring warm, moist Gulf air into the Plains and Midwest. It will also leave us very closer to the more active flow in the jet stream, meaning showers and thunderstorms could be possible. The first of those will arrive Monday morning, but then again could develop late Monday evening into Tuesday. Even though temperatures are expected to warm, showers and thunderstorms during the day could limit just *how* warm it gets through the week. The days are not expected to be a washout, however, as the best day for storm activity appears to be Thursday evening/night ahead of a cold front.