A dome of cold, dry air has dropped into the Heartland, bringing a morning low of 14 degrees F to central Missouri. Across the Midwest, temperatures range from the teens to 20 below zero, with dew points from the single digits to near 30 below. Sunny skies accompany the dome but the low angle of the winter sun produces little warmth.
Along the southern edge of this dome, from east Texas to the Florida Panhandle, a clash with warm, humid air is producing heavy rain and flooding. Dew points across this boundary rise by 50 degrees in some areas, from the mid teens in Arkansas in the mid sixties along the Gulf Coast. As the dense, cold air knifes below the warm, soupy air, the latter is forced to rise, dropping its temperature below the dew point and triggering the heavy rain. Since the boundary is stationary, this precipitation continues to fall over the same areas and flooding results.
A milder, Pacific high will nudge this dome to the northeast over the next few days and the Midwest should return to more seasonal conditions. But, from now until mid March, these polar outbreaks will invade the Heartland on a regular basis.
