Looking at water vapour imagery this evening, can see that there is another short wave trough embedded within the broad upper low/500 mb flow pushing in through southern BX this evening. This shortwave is forcast to push into south central SK tomorrow afternoon/evening which will bring the risk of severe weather for the extreme southeastern portion of SK and southwestern MB. Along with this short wave is 500 mb wjet core of 50-55 kt and a 250 mb jet core of around 100 kt which will help provide ample upper level divergence within the unstable air mass.

At the surface a low which is currently developing in northern MT/southern AB associated with the upper shortwave is forecast to track along the US/Can border and be located roughly between Estevan, SK and Minot, ND by tomorrow afternoon. Most models are in good agreement with where the low will be located the real disagreement comes with where exactly the warm front will be placed. By the looks of the 500 mb flow being a little more zonal I would think that the NAM solution having the front roughly along the TCH seems to be the more valid solution as opposed to the GEM/GFS idea of pushing the warm front into the interlake region. But will emphasize that where the front is located will make all the difference as to where the severe weather threat exists for tomorrow as all the instability needed will follow in behind the warm front along with very rich theta-e air. Within the warm sector the good flow aloft will bring 40-50 kt of surface to 500 mb bulk shear, south easterly 850 mb winds will make for about 20 kt of sfc to 850 bulk shear, and 2000-3000 J/kg os SBCAPE looks to be enough to get rotating updrafts. Low level shear will also be enhanced in the vicinity of the warm front also, thus any storms that do initiate, is they manage to anchor to the warm front there would be a tornado threat. One issue I do see is how ongoing convection tonight in SK will affect day time heating and that shear vectors are not exactly in a favourable orientation to allow for real discrete cells. Soundings also show a little bit of a CAP issue once again but hodographs are favourably veered within a relatively deep layer. Thus I believe convection will be rather messy tomorrow afternoon (initiate be around 3-5 pm CDT) but within the mess embedded mesos/supercells are possible and even a brief tornado. The purple region indicates general t-storm risk area and green shows where I think rotating storms are possible along with a brief tornado risk. Green region includes Brandon, MB, Moosomin, SK, Estevan, KS.

For comparison sake, here is the GFS sfc forecast for the same period, it is very similar to the GEM thus I'll just show the GFS forecast. This this were to verrify with the frontal postion then Winnipeg and Portage La Prairie would also be included within the green region and the lake breezes would become more of a facotor with possible additional initiation ahead of the main line.