Figure 1 shows the surface observations at 7:00 am CDT, which shows a cold front moving through southern Manitoba. Some showers are also observed behind the cold front in the Westman area. It is possible that some of these showers produced a brief spinup near Grandview.
According to Environment and Climate Change Canada (2018), an F0 tornado touched down at 8:00 pm CDT near Grandview, MB. The track and width of this tornado was not documented by ECCC. The tornado caused no injuries, fatalities or property damage.
Sources
NOAA Central Library. (2020). U.S. Daily Weather Maps. Thursday July 2, 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/