Extratropical Cyclones Forming East of the Rocky Mountains

Edition 1 - Example of Rocky Mountain Cyclone Surface Dewpoint Temperature of the April 2001 Cyclone - The cyclone transports moisture northward east of the low and dry air southward west of the low. Note that early in the animation, moist air (dewpoint temperatures above 50° F) is present across much of the eastern United States. As the cyclone develops and moves northeastward, drier air from Canada is transported into the central U.S. After the cyclone moves into Canada dewpoint temperatures less than 50° F prevail across all of the U.S. except in the extreme southeast.