One of the reasons this storm was such a prolific snowmaker was that it tapped into a rich source of tropical moisture from all the way south in the Bahamas. (mashable.com)
From the 19th of June through the 21st, a slow moving low pressure system tapped into tropical moisture from the Gulf of Mexico and delivered extreme rainfall to the foothills and front ranges of the Rocky Mountains. (pacificclimate.org)
Fueled by tropical moisture drawn north and pinned over the area by a stalled weather pattern, the amount of precipitation between Sept. 9 and 15 in some areas was more than what typically falls in an entire year. (discovermagazine.com)