A low pressure system crossing the province will bring hot and unsettled conditions to southern Manitoba today. The heat will be short-lived, though, as a cold front ushers seasonal temperatures back into the region for Wednesday.

In the wake of a warm front that moved through overnight, temperatures will soar into the upper 20s and low 30s across southern Manitoba today. Alongside the heat, humidity levels will also climb through the day, reaching fairly muggy levels by the evening.

Thunderstorm activity will be the most notable, and challenging, weather of the day. There will be several features moving through the region that that may support thunderstorms today. The first will be an area of showers and thunderstorms — the remnants of overnight convection — that will continue eastwards through the Interlake. This activity will weaken as the morning progresses. While most of it should stay north of the Red River Valley, the southern edge might clip along the Trans-Canada Highway corridor. The second feature will be the warm front itself, which may have some ongoing thunderstorms along it this morning. Any activity along it should shift eastwards into the Whiteshell and then weaken.

Once all the morning activity pushes out, the Red River Valley will see more sun as things heat up. Later in the day, a risk of severe thunderstorms will develop as several features begin pushing across southern Manitoba. Both the low centre, warm-sector trough, and cold front could support thunderstorm development later today. The heat and humidity will combine with favourable winds aloft to pose a notable risk of severe weather.

The combination of energy (from the humidity and instability) and shear (from how winds change with height) is highly favourable for severe thunderstorm activity across southern Manitoba today. The biggest uncertainty with storms in the afternoon/evening will be whether or not they actually develop. A layer of warm air aloft will keep storms down until late in the day. It seems likely that the forcing will be strong enough by evening for isolated to scattered thunderstorm development. The activity will likely begin in the southwest and push into the Red River Valley. These thunderstorms would be capable of producing damaging wind gusts, damaging hail, and torrential rain. In addition, an isolated tornado or two may be possible with these thunderstorms as well.

The last unknown related to thunderstorm development will be exactly how warm temperatures end up. Satellite imagery yesterday evening showed a fair amount of high-level smoke moving eastwards from fires over southern British Columbia. If that smoke inhibits temperatures even a couple degrees, that could be enough to thwart thunderstorm development. All those things being taken into account, the weather later today is a bit of an unknown. It will be important to stay up to date on any watches or warnings issued by ECCC later today.

The thunderstorm threat will diminish in the evening as temperatures fall to a low in the mid-teens. Winnipeg will see pleasant conditions on Wednesday with clearing skies, breezy northwest winds, and a high in the low 20s. On Thursday, breezy southerlies will push a warm front northwards and send highs back into the upper 20s. Thursday night might be very warm with southerlies continuing and lows warmer than 20 °C possible.

Long Range Outlook

Friday could bring some morning showers or thunderstorms to the Red River Valley, followed by mixed skies and a high in the upper 20s again. It might also get humid on Friday as well.  A cold front will sweep through by Friday evening, ushering cooler temperatures back into the region for the weekend. Highs will likely sit in the low 20s with lows in the low to mid-teens on Saturday and Sunday. A few showers might be possible on Sunday as well.

Next week is looking like it will start off with near-seasonal temperatures and plenty of sunshine.

Today’s seasonal daytime high in Winnipeg is 26 °C while the seasonal overnight low is 13 °C.