It's been two weeks since September's only rainfall was recorded at O'Hare International Airport, Chicago's official observing site. It won't take much rain to exceed our entire monthly total of 0.03 inch. The high pressure regime that has produced an almost steady east wind along with the dry conditions and mild temperatures is finally breaking down. A low pressure system is set to establish itself over the Rockies and influence weather over the Midwest this week. A southerly flow up the Mississippi River Valley should feed warm, moisture-laden air into Illinois, resulting in considerable cloudiness. Even though showers or thunderstorms will probably not occur every day, it will be difficult for meteorologists to leave rain out of the daily forecasts.
Eastern U.S: A land of contrasts
The upper-air blocking pattern has persistently held the center of cold high pressure over the Northeast. Sunday morning frost and freeze advisories were posted for most New England states as well as northern lower Michigan. Meanwhile, persistent low pressure to the south has resulted in record heavy rains and flooding over the Gulf Coast the past week. Atlanta was among the latest, reporting a record daily rainfall of 3.7 inches Saturday.
