The U. S. National Weather Service is warning that rain, rising temperatures and thick fog could lead to flooding in the midwestern United States Saturday after days of cold weather, heavy snow and ice.

The Weather Service issued flood watches and warnings for parts of the states of Illinois, Indiana, Iowa, Michigan, Missouri and Wisconsin.

Heavy fog grounded all flights at the Midway airport in Chicago, Illinois, Friday night, and there were more than 400 cancellations at the city's O'Hare airport, a major travel hub.

A warm front is also entering the northwestern United States. Rain in some parts of Oregon and Washington is expected to wash away much of this week's massive snowfall and could cause flooding.

Snow warnings are still in effect in other parts of Oregon, Washington, and many other states.

Some information for this report was provided by AP.