Damaging derecho roars into Chicago area during Monday evening commute period; storm gusts hit 80-mph downing trees, flipping semis and knocking power out to 175-thousand



Its powerful winds flipped semis, uprooted huge trees—some with trunks more than 2 feet in diameter, tossing them across homes like matchsticks— while taking down power lines, producing electrical outages which affected 175,000. The damaging derecho, which roared across the Chicago area, reaching the city in the final hour of Monday’s busy evening commute period, turned late afternoon skies to night, racing across the area at high speed, exiting just as quickly. In many areas, the system’s highest winds spanned all of 10 to 15 minutes giving way expeditiously to lingering downpours and far gentler breezes.



But the rush of high winds hit with devastating effect, producing a swath of damage which reached across a series of states from just east of the Rockies into the Midwest, including northern Illinois and Indiana.



Monday’s high-speed squall line moved as fast as any which have swept this area and ended up covering 950 miles of terrain in its 25-hour trek from the high plains of eastern Colorado, where it first sprang to life just before 5 pm Sunday evening, into and across the Chicago area, eastward into Indiana and Ohio.



The Storm Prediction Center defines derechos as widespread, long-lived wind storms associated with a rapidly moving band of thunderstorms. The bowed, arc-like appearance of derechos on radar displays is viewed as a tell-tale sign the thunderstorms which comprise such systems are generating damaging straight-line winds.

Photo courtesy of Picture Ron Smierciak, Griffith, Ind.

Photo courtesy of Picture Ron Smierciak, Griffith, Ind.



Atmosphere primed for significant new t-storm eruptions Tuesday and Wednesday as “ring of fire” pattern rolls on….



The storm threat is far from over Tuesday and Wednesday and the Chicago area is outlooked for potential additional severe thunderstorm development both days.



The environment across the Midwest remains very warm and is loaded with tropical moisture—elements which fuel thunderstorm development.


Powerful upper winds rotating around the northern periphery of a dome of hot air centered in the Plains and Midwest, threaten to transport new thunderstorm clusters into and across the Chicago area, energizing these storms and encouraging high-wind production in the process.




It’s a classic “ring of fire” pattern—an atmospheric set-up which features intense storm clusters which race along the northern flank of hot air masses, embedded within  powerful upper winds which develop as result of the wide temperature variation between the dome of heat and the cooler air which resides to the north.




O’Hare’s 89 Monday ranks as June’s warmest; 2013’s 2nd warmest




Monday’s 89-degree high at O’Hare was June 2013’s warmest to date and the 2nd warmest temperature thus far this year. Peak readings Tuesday and Wednesday will return to the same level, extending the warm spell deeper into the coming week.




Thundery downpours could yield big rain tallies in coming days




Model rainfall forecasts reflect the varied nature of summer precipitation distribution.  But, with multiple storm clusters likely to traverse the Chicago area in coming days, the predicted totals are impressive.




A suite of model rain projections generated over recent days by a group of forecast models indicates average totals may approach  2″ but that the spread in potential 3-day amounts could range from 0.78″ to as much as 6.35″.