A strong line of thunderstorms ripped through the Rock River Valley early Monday morning leaving downed limbs and minor wind damage in its wake.
Temps will hover in the high 80s-low 90s through the afternoon with heat indexes reaching over 100F in some portions of the area, creating unstable atmospheric conditions suitable for strong storms to develop.
A second round of storms is expected to form Monday afternoon into the evening as an upper level ridge continues to feed warm moist air into the region.
The National Weather Service’s Storm Prediction Center has placed much of northern Illinois under a Moderate Risk for severe storms for Monday afternoon/evening. Other outlying areas are at an Enhanced Risk.
The first Severe Thunderstorm Watches in the area were issued in southern Wisconsin after 3 p.m.
Popcorn-type scattered storms are expected during the afternoon, some producing high winds and hail. Another strong line of thunderstorms is expected in the evening hours, moving into the area from the northwest.
NWS also warns that the chance for tornadic activity is highest stretching in a band from the northwest corner of the state to the south and southwest suburbs of Chicago.
A Tornado Watch has been issued for Winnebago, Boone, Carroll, DeKalb, Jo Daviess, Lee, McHenry, Ogle, Stephenson and Whiteside Counties until 11 p.m.
Areas along the I-39 corridor and western I-80 corridor should be on alert for the possibility of tornado producing storms developing throughout Monday afternoon/evening.
The tornado outlook prediction throughout the northern Illinois area is at the same level as during the build up to the April 9 storm which spawned the Rochelle/Fairdale tornado.
The formation of a derecho is also possible, bringing damaging straight line winds in excess of 60-80 mph at times.
A Flash Flood Watch is in effect through 1 a.m. Tuesday.
Please remain advised to current conditions and pay attention to any developing weather situations throughout the afternoon. Area residents are recommended to check their weather radios and engage alerts on their cell phones or other mobile devices.
Take cover as soon as warned to or if you feel conditions warrant. Remember, relying solely on tornado sirens during severe weather outbreaks can be dangerous.