Why Nepal's rare, deadly flood struck without warning

A rare flash flood in Nepal struck without warning under clear skies, leaving hundreds dead and thousands missing. Nepali officials reported nearly 700 deaths and about 3,000 missing near the Nepal-China border. The disaster highlights gaps in warning systems, which typically monitor rain and rivers, not glacier-driven collapses. Similar "blue-sky floods" have occurred in the U.S., including Washington state in 2001.