Synchronous outbreaks.

Start year and end year of synchronous (i.e., outbreaks occurring simultaneously in three or more regions) period, duration (years) of synchronous outbreak, and individual regions recording an outbreak in at least one year during the period. Regions are as follows: BC = central British Columbia, WA = northern Washington, MT = western Montana / eastern Idaho, ID = western Idaho / northeastern Oregon, OR = north-central Oregon, CO = southern Colorado, NM = northern New Mexico. Note: the New Mexico record ends in 1990, in the midst of a widespread outbreak.