A large mesoscale convective system (MCS) is continuing to impact parts of Manitoba and North Dakota this morning as depicted in the above satellite imagery. The threat in Manitoba today for severe thunderstorms, supercells and possible tornadoes are conditional to airmass recovery throughout the afternoon behind this MCS.
The warm front (depicted above as red) will continue to lift north towards the MB/ND border later this afternoon. This should allow warm/moist air to invade southern Manitoba this afternoon and enhance low-level shear in the area. The key for storm initiation today will be an outflow boundary left behind by the currently ongoing MCS. This outflow boundary can be seen below:
This outflow boundary should initiate new storms in southeastern Saskatchewan and southwestern Manitoba throughout the early afternoon. This causes a problem for the severe weather potential. With little airmass recovery after the MCS, little to no instability will be able to build up prior to those storms developing. In this scenario, it would mean these storms will likely NOT be as severe as some may expect for today. These should be fairly elevated in nature as well with limited severe weather threat.
Another scenario is depicted above. In this scenario, there was some airmass recovery prior to storm development. Essentially, the atmosphere was able to "cook" for a few hours, allowing instability to build up on southern Manitoba. Storms would initiate in SE Saskatchewan SW Manitoba still and merge into a squall line. Storms may become supercells early in their life-cycle. As they interact with the escarpment and with the outflow boundary left by the MCS, they may begin to rotate and a tornado threat is possible. The tornado threat will be maximized in southwestern Manitoba in the afternoon. In the evening, a line of storm may impact Portage La Prairie and Winnipeg late evening through the night.
Area(s): Southern Timing: Late Saturday afternoon and evening, possibly overnight in the extreme southeast.
Threats: 3 to 5 cm hail, wind gusts 90 to 120 km/h and local rainfall amounts of 50 to 75 mm.
Possible tornado in southwestern portion of the province from the Red River Valley to the Saskatchewan border.
A trough of low pressure will intersect with a hot and humid airmass over southern Manitoba allowing for the development of severe thunderstorms late this afternoon and into the night. Some thunderstorms will become very intense capable of producing 4 cm hail, heavy downpours, and even tornadoes across southern sections.