Figure 1 depicts the surface observations at 10:00 am CDT, which shows a trough of low pressure moving east across southeastern Saskatchewan. This trough was the focus for thunderstorms at it moved east across southern Manitoba, which ultimately led to this tornado.

According to Environment and Climate Change Canada (2018), an F0 tornado touched down at 12:35 pm CDT near Sandy Lake, MB. The path and width of the tornado was not documented by ECCC. The tornado caused no fatalities, injuries or property damage.
Sources
NWS Weather Prediction Center Surface Analysis Archive. (2017). Surface analysis 15Z Sat Jul 3 1999. 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/