Tonight could very well be a very active night across southern Manitoba as a frontal system that developed out in Western Saskatchewan will move into southern Manitoba overnight, it appears that it is already on the doorstep accorddingg to this Rain Alarm image. The low pressure system will slide eastwards gradually bringing the warm front northwards as it moves East, which means that the severe potential will be north of the border rather than it being south of the border in which many ways it has before.
For the night ahead with the convection already developed the severe potential will increase substantially as all of the necessary ingredients including enough shear flow into the developing storm. Let's look over the ingredients using Brad's mist principle.
Moisture: No shortage of mositure dewpoints will skyrocket overnight into the mid to high teens
Instability: Lots of it should support thunderstorm sustaining CAPES on the order of 2,000 to 3,000 J/kg, LI's -5 to -10, Total Totals of 57 in Winnipeg, K Index of 41 in Winnipeg, Sweat Index of 494 in Winnipeg, BRN of 14 in Winnipeg K index of 46 in Brandon, Total Totals of 60 in Brandon, K index of 14 in Brandon, SWEAT index of 662 in Brandon. Here is what they all mean...
Shear: Enough to support bow echos and development and organization of storm cells. Bulk Shear from 50 to 75 knots. Storm Relative helicity 200 to 450 m2 s2.
Trigger: Frontal system arriving from the west with warm front slowly moving northwards during the overnight.
The severe weather threat will involve a development of a squall line of thunderstorms that will travel through southern manitoba in the coming hours, with the potential of bow echo development which could very well evolve. Factoring in all things the main concerns will be a hail and wind threat, with high levels of moisture in the atmosphere there is a risk for severe flooding and torrential downpours. Hail will also be a concern with sizes up to golfballs once again expected, and if the storms become outflow dominant there very well could bring gusts in excess of 100km/h. Frequent lightning will also be a concern with the potential for dangerous cloud to ground strikes.
The timeline of the storms will vary on speed of the system, it looks like the southwest will be hit after midnight, Red River Valley at around 3am, Eastman early morning and Northwest Ontario during the day.
Severe Weather Threat: Large Hail as Large as Golf Balls, Frequent lightning, Flooding torrential rains, Damaging winds as high as 100km/h or more. No Tornadoes risk is low however.
More Storms Expected during the day Sunday, some may be severe as well.
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