Figure 1 depicts the surface observations at 7:00 am EST, which shows an area of high pressure across the Pacific Northwest and a trough of low pressure off the coast of British Columbia. It is likely that this trough moved inland and triggered storms on the lee side of the Rockies, which ultimately resulted in this tornado.
According to Environment and Climate Change Canada (2018), an F0 tornado touched down at 6:45 pm MDT near Clandonald, AB. The path and width of the tornado was not documented by ECCC. No property damage was documented for this tornado.
NOAA Central Library. (2019). U.S. Daily Weather Maps. Friday June 5, 1981 [PDF]. Retrieved from https://library.noaa.gov/Collections/Digital-Collections/US-Daily-Weather-Maps
Environment and Climate Change Canada Data. (2018). Canadian National Tornado Database: Verified Events (1980-2009) – Public. Retrieved from: http://donnees.ec.gc.ca/data/weather/products/canadian-national-tornado-database-verified-events-1980-2009-public/