Figure 1 depicts the surface observations at 7:00 am EST, which shows a stationary front across Alberta. This front triggered thunderstorms, which ultimately led to this tornado.

According to Environment and Climate Change Canada (2018), an F0 tornado touched down at 12:45 pm MDT near Herronton, AB. The path and width of the tornado was not documented by ECCC. The tornado resulted in one injury.
Sources
NOAA Central Library. (2019). U.S. Daily Weather Maps. Friday July 21, 1984 [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/