WeatherBug (https://www.weatherbug.com/) is a public web service that provides updated weather forecasts across North America, as well as in other countries. The service hosts a multitude of publicly available webcams throughout the U.S that provides viewers with time lapse footage of the current weather in a specific location. Each image is taken at 30 minute intervals over 24 hours.
The following document contains a compiled list of webcams from WeatherBug that provide a fairly flat horizon line, and a clear view of the foreground.