The overlapping weather systems could result in life-threatening flooding, with some areas potentially receiving 10 to 20 inches of rain. Vulnerable locations include saturated grounds, dry washes, burn scars, slot canyons, and higher terrains, where flooding may occur rapidly even without direct rainfall. More than 15 million people are at risk, particularly in Arizona, New Mexico, southern Colorado, the Texas Panhandle, and southwestern Kansas. Residents in these areas are urged to remain vigilant as conditions may deteriorate quickly, especially in flood-prone zones.