Figure 1 shows the surface observations at 1:00 pm CDT, which shows easterly flow across southern Manitoba. This flow became more northerly throughout the day and could have triggered storms near Oakbank along a lake-breeze boundary coming off Lake Winnipeg.
According to Environment and Climate Change Canada (2018), an F1 tornado touched down at 5:00 pm CDT near Ste. Genevieve, MB. The path and width of the tornado was not documented by ECCC. The tornado caused no fatalities or property damage, but caused 3 injuries.
NWS Weather Prediction Center Surface Analysis Archive. (2017). Surface analysis 18Z Sat May 25 1985. Retrieved from: https://www.wpc.ncep.noaa.gov/archives/web_pages/sfc/sfc_archive.php
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/