Severe Weather possible for southern Manitoba, this evening.

Much of southern Manitoba is at risk for severe weather late this afternoon into this evening.

Southern Manitoba will be under the influence of a southerly flow today with temperatures reaching into the mid to high 20's with humidex values near and around 38 to 42C. An approaching trough and cold front to the west of our area will encounter the warm and humid airmass that is in place allowing a potential for powerful storms to occur. Let's have a look at the data.

Moisture: Dewpoints will be in the 18 to 21C range, for the most part with a chance for a few areas to have dewpoints about near 25C. Ample moisture will be in place. The question is the capping, because the moisture and heat may rise high enough in mid levels to prevent storms from forming. The cold front may or may not be sufficent to allow for enough cooling to occur at mid levels. And allow the cap to break.

Shear: Definitely not lacking at all, EHI values of 3 to 5 and Helicity mainly the highest west of Winnipeg into the Red River Valley around 8pmish 300 to 500 m2/s-2. Supercelluar structure is definitely possible, and or high winds. Sufficient enough for storm organization.

Instability: Sufficient instability will be in place for southern Manitoba this afternoon/evening, mlcapes and SBCapea will be on the order of 3,000 to near 5,000. With Lifted indices on the order of -7 to -10.

Trigger: The cold front will be coming in from southeastern Saskatchewan and moving into southwestern Manitoba over the next few hours into the Red River Valley area by the evening. Should provide focus for convective development as well as possible supercells.


The environment in place will end up resulting in severe thunderstorm/supercells formation somewhere between Brandon and the area east of Winnipeg, all depending on the timing of storms firing. If Storms do manage to form there will be a chance for discrete supercells to occur and pose a tornado threat. There is around 1 million or so people in that risk area for tornadic development, including Brandon and Winnipeg. There is a risk for hail up to golfball and or baseball size hail to occur, Once storms organize later on this evening the threat for damaging winds could be present with an ongoing large hail threat (up to baseball size hail), wind threat for winds over 100km/h, rainfall potential up to 50mm or more, and frequent dangerous lightning. Storm threat should ease up somewhat as storms travel into Northwest Ontario or southeastern Manitoba depending on where they form.

I will keep you updated as the evening goes on. -Mike