Severe thunderstorm risk for parts of Prairies, here's where
Meteorologist
Tuesday, June 27, 2017, 10:59 AM - An active weather pattern is underway for the Prairies, with a widespread risk of thunderstorms Tuesday.
While southern Edmonton stayed clear of most of the severe weather Monday, Edmonton Namao Heliport recorded a wind gust of 100 km/h with some reports of 2 cm hail in northern areas.
It's all courtesy of an upper level trough that will continue to push east, bringing with it moist and unstable Pacific air in the lower levels of the atmosphere.
KEEP ON TOP OF ACTIVE WEATHER: Visit the Alerts section of the website
The trough will push into central and eastern Saskatchewan through the day Tuesday, and then gradually into southern Manitoba through the evening and overnight hours.
Ahead of the upper trough winds from the south through the lower levels of the atmosphere will bring a moist and unstable airmass into eastern Saskatchewan and southern Manitoba as shown below.
At the same time through the mid-levels of the atmosphere the warm air pushing northward will bring in what's known as a capping inversion. The graphic below was produced by the Sioux Falls, South Dakota. This forecast office in the U.S. but offers a great explanation as to what a capping inversion (also called a CAP) is and why it prevents thunderstorm development.
What one factor that could prevent or limit more thunderstorms later today? Something we call "The Cap". Here's a look. pic.twitter.com/YyVVljPDkt
— NWS Sioux Falls (@NWSSiouxFalls) June 21, 2017
The focus for any severe thunderstorms to develop will be on southeastern Saskatchewan across the hatched area outlined below.
The threat has been downgraded to just some isolated severe, due to a lot more cloud cover coming out of Alberta, which may hinder the amount of instability through the afternoon. The CAP may not allow any storms to develop until the late afternoon/early evening after instability has peaked.
If storms can initiate early enough in this region then some storms could become severe. Wind shear may be favourable for a few supercells and perhaps an isolated tornado risk. Again, this will be dependent on the CAP breaking and storms firing early enough.
South-central Manitoba - areas from Brandon eastward through Winnipeg - are expected to see widespread rain and thunderstorm activity overnight into Wednesday morning.
Here, the capping inversion will keep a tight lid on things and really won’t get any lift until the warm front and strong southerly winds begin to push in to the south-central part of the province. Once the warm front and strong southerly winds do move in, scattered thunderstorms will spread across the region. An isolated severe storm or two is possible with the main threat being heavy rain and strong winds.
Across central and northern Alberta, the upper level low will linger, as will the risk for scattered thunderstorms. These should be mainly non-severe with the risk for small hail and heavy rain. However, as is the case with most upper level low systems in Alberta, the potential will be there for funnel clouds to develop across the risk area.
On Wednesday, the upper trough may sag south, bringing the risk of cold core funnel clouds.
Check back for updates as we continue to monitor the system.