Weather Underground Forecast for Saturday, July 21, 2012. More showers and thunderstorms are anticipated in the East, as well as the Upper Midwest and Great Lakes on Saturday. A low-pressure system moving through Canada will continue pushing a cold front eastward through the Upper Midwest and Great Lakes. This will produce more showers and thunderstorms, some of which may turn severe with strong winds and large hail. The forecast for noon, Saturday, July 21, 2012 shows a frontal boundary lingers over the Southeast, kicking up scattered showers and thunderstorms from the Gulf coast through the Mid-Atlantic states. Meanwhile, thunderstorms develop over the Northern Plains and Upper Midwest. (AP Photo/Weather Underground) Close South of this frontal boundary, expect hot conditions to persist from the Central and Southern Plains through the Mid-Mississippi River Valley. Excessive heat advisories will remain in effect from the Central and Southern Plains, through the Midwest and Mid-Mississippi River Valley as high temperatures will reach into the lower 100s. In the Southeast, a frontal boundary extends from the Gulf states through the Mid-Atlantic states, producing more showers and thunderstorms throughout the day. These storms will create more heavy rainfall and strong winds. Severe thunderstorms development is likely from eastern Texas through Mississippi. Expect rainfall totals to range from 2 to 3 inches in areas of strong thunderstorm development. Out West, monsoonal moisture will maintain thunderstorm development over the Central and Southern Rockies, as well as the Southwest. However, a ridge of high pressure builds up the West Coast on Saturday, allowing for warm and sunny conditions return.