Wednesday, October 6, 2010

From One Extreme to the Other!

Local weather stations today had a roller-coaster ride on the temperature scale! After lows reached the 30s for many locations, highs reached 80 degrees or more! Rochelle, for example, had a morning low of 35 and an afternoon high of 80. Sterling recorded an even higher range in temperature with a low of 34 and a high of 81! And temperatures at the Rockford Airport started-out at 39, then rose to 81 for a high. Our normal high and low are 67 and 44 for this date. So we would typically see a range in temperature of 23 degrees, not the 47 degree swing we saw today in some locations!

There are three reasons we cooled down so much last night and heated up so quickly this afternoon. One has to do with the lack of moisture in the air. Dry air heats-up and cools down more quickly than moist air. Another reason is the sunshine, which is pretty self-explanatory. Finally, the lack of wind last night allowed the cold, dense air to settle near the surface. Then the winds picked-up during the afternoon, mixing this cold layer out quickly and allowing upper-level air to descend to ground-level and heat by compression. Stay tuned... We may hit 80 degrees again a time or two by the end of the week!  --TS

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