IDAHO FALLS, Idaho (KIFI)- A heat advisory is in effect until 11 p.m. tonight for much of southern Idaho. The heat advisory covers the Eastern Magic Valley, Shoshone, the Arco and Mud Lake Desert, the Blackfoot Mountains and the Snake River Plain. Monday and Tuesday are forecast to remain sunny with high temperatures near 93 degrees. Weather forecasters expect a cooling trend to begin Sunday and continue through the upcoming week as an upper weather ridge flattens. High temperatures are projected to fall below normal levels by Thursday.