Boulder County says nearly half still unaccounted for . Boulder saw only 4 its a single day rainfall in annual . A stream of unusually humid air that was sweeping over the area early last week helped fuel the storms . `` It all happened fairly quickly , '' a scientist says . Nebraska warily watches the rising the South Platte River .
Boulder County says nearly half still unaccounted for . Boulder saw only 4 its a single day rainfall in annual . `` It all happened fairly quickly , '' a scientist says . Nebraska warily watches the rising the South Platte River .