Figure 1 depicts the surface observations at 1:00 pm CDT, which shows an area of high pressure across southern Saskatchewan and a low pressure system over Wisconsin with a trough of low pressure extending northwest across northwestern Ontario. It is possible that the trough extended across the Interlakes Region of Manitoba and/or a lake-breeze boundary from Lake Winnipeg triggered thunderstorms, which ultimately led to this tornado.
According to Environment and Climate Change Canada (2018), an F0 tornado touched down at 3:00 pm CDT near Morweena, MB. The path and width of the tornado was not documented by ECCC. The tornado caused no fatalities, injuries or documented property damage.
NWS Weather Prediction Center Surface Analysis Archive. (2017). Surface analysis 18Z Fri Aug 1 2003. 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/