These are the built-in preset regions:

Global - The entire Earth.
Lower 48 - The Contiguous U.S.
Northeast - U.S. states of PA, NJ, NY, NH, VT, MA, CT, RI, and ME.
Europe - Continental Europe, British Isles, Iceland, and European Arctic Islands.
Asia - Continental Asia, Japan, Phillipines, and Sri Lanka.
North America - Canada, Continental U.S. (incl Alaska), Mexico, and Central America.
South America - Continental South America and Falkland Islands.
Africa - Continental Africa, Cabo Verde, and Madagascar.
US_Canada - All of the U.S. and Canada, including Alaska and Hawai'i.
Colorado Basin - The entire Colorado River Basin.
AlaskaNWCanada - Alaska and the part of Canada that collaborate on quarterly climate outlooks.
NAtlantic30 - The Atlantic Ocean Basin (incl Carribbean and Gulf of Mexico) from 0N to 30N.
NAtlantic50 - The Atlantic Ocean Basin (incl Carribbean and Gulf of Mexico) from 0N to 50N.
Land60N - All global land from 60N to 90N.
PacificNorthwest - The entire states of Washington, Oregon, and Idaho.