Flash flooding is a major concern across the Desert Southwest, including urban areas like Los Angeles, San Diego, and Las Vegas. National parks in the region are also at risk, with visitors advised to postpone plans until conditions improve. In the northern Rockies, heavy snowfall is creating hazardous travel conditions. In Mexico, Hurricane Simon is expected to cause significant damage along the west-central coast, including Puerto Vallarta, with risks of landslides and flooding from torrential rain. The storm surge and high winds could lead to widespread destruction in affected areas.