Figure 1 shows the surface observations at 7:00 pm CDT, which shows a low pressure system over southern Manitoba with an occluded front extending south into North Dakota. The counter-clockwise flow of the low brought moist/warm air from the south across Westman. This warm/moist air, combined with terrain influences from the Manitoba Escarpment, triggered supercells across western Manitoba, which ultimately led to this F1 tornado.
According to Environment and Climate Change Canada (2018), an F1 tornado touched down at 7:00 pm CDT near Pleasant Valley Reservoir, MB. The track and width of the tornado was not documented by ECCC. The tornado caused no fatalities, injuries or property damage.
NWS Weather Prediction Center Surface Analysis Archive. (2017). Surface analysis 00Z Thu Aug 6 1987. 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/