La Nina conditions have developed in the central Pacific Ocean. La Nina is defined as the periodic cooling of sea surface temperatures in the east-central equatorial Pacific Ocean. The current La Nina is forecast to strengthen through the fall and persist into 2011.
La Nina episodes usually affect weather patterns across the country. This is due to variations in the jet stream pattern caused by the cooler-than-normal sea surface temperatures. Historically across much of the Midwest, La Nina episodes have resulted in warmer and drier than normal conditions in the fall, and colder and wetter-than-normal conditions in winter.
In the near-term , a quiet stretch of weather is underway. A cold front will pass through the region on Tuesday. Expect cooler temperatures for Wednesday and Thursday.