I'll do a de-brief on this in more detail at 4pm, but last night's rippin' winds were caused by what's known as a wake low. Put simply, behind a line of showers, occasioanly a stronger-than-normal sinking motion heats the air, and creates an area of lower pressure. Ahead of that same line, a small high pressure is common. This causes a flow from the high to the low (south last night) which can be quite strong depending on the strength of the low. Milwaukee Airport Terminal radar showed winds of 70 knots 800 feet above the ground in most of Kenosha and Lake Counties last night around 11pm. That area of intense wind migrated southward into Kane, Cook and DuPage Counties before weakening overnight. Gusts reached 55 mph at Waukegan, 50+ at Streamwood, Addison, Portage, Elgin and Hampshire. At O'Hare, a 46-mph gust was recorded. Many folks lost tree limbs or had to collect their lawn furniture after last night's blow.
A few storms will fire again this afternoon, especially south of the city. Less humid air will filter in fromt he north for tomorrow.
Mike
