Cooldown Due After 70s Today

Gusty winds from the southwest will boost temperatures into the70s today. Moisture from the Gulf of Mexico will also move into theMidwest, giving much of Illinois the threat of showers andthunderstorms this afternoon.

If enough energy in the upper atmosphere joins with thelow-level warm and humid air, some of these storms could becomestrong or severe late this afternoon and this evening.

A weak cool front is due Friday, with a continuing chance ofshowers and thundershowers. The rather complex weather system willmove east Saturday, ending the threat of showers and ushering inslightly cooler temperatures.The main body of chilly air will stay well north of Chicago,but it might be a good idea to take along a light jacket thisweekend.Overall, the jet stream pattern suggests temperatures willaverage near or slightly above average, with more frequent showeryspells into next week. Another low pressure system is expected tomove into the area by next Tuesday with more welcome rainfall.Tom Bobula is filling in for Paul Douglas.Weather QuizWhich of the following is the best absolute measure of atmosphericmoisture?A) Relative humidityB) Dew pointC) Cloud metersD) Rain bucketsAnswer: (B) Dew point is the temperature to which air must becooled for saturation to occur. Relative humidity is the second-bestmeasure of moisture, but as the name implies, is relative to thecurrent temperature.Weather FactSevere thunderstorms are defined as having one or more of thefollowing: tornadoes, winds of 58 m.p.h. or greater, significant winddamage, or hail 3/4; - inch diameter or larger.;