Widespread and potentially catastrophic areal flooding and river flooding is expected this afternoon through Wednesday morning in Eastern Oklahoma, Western Arkansas, Western Louisiana, and Southwest Missouri, warns the National Weather Service in Tulsa, Oklahoma, in their latest flood watch for the region. The storm system responsible is a massive, slow-moving trough of low pressure over the Western U.S. that dumped heavy snows that closed several interstate highways in Arizona over the weekend. This storm system will collide with the warmest and moistest air mass ever recorded in March in the Central and Eastern U.S. According to the NWS in Minneapolis, Minnesota, moisture flowing northwards into Minnesota along the cold front yesterday had the highest levels of moisture ever recorded so early in the year, and moisture levels are expected to remain at record levels today. At the boundary between the Western U.S. trough of low pressure and Central U.S. ridge of high pressure, a cold front will lift huge quantities of moisture-laden air aloft, forcing record rains to fall. A wide region of 4 – 8 inches of rain is expected in the flood watch area, and isolated amounts as high as 15 inches could fall by Wednesday, as numerous rounds of thunderstorms repeatedly track over the same area.
The source article Tornadoes, extreme flooding, unprecedented heat expected in U.S. today : Weather Underground was published March 19, 2012 by Weather Underground: Dr. Jeff Masters' WunderBlog .