Conditions will turn unsettled over southern Manitoba as a deep upper trough develops over western North America this weekend.
The weather will change over the next few days as an upper low off the west coast moves onshore. As it moves into British Columbia, an upper trough will dig southwards over the Rockies. As it does, it will turn a relatively benign pattern over the Prairies into something much more unsettled.
After a beautiful Friday with temperatures climbing into the mid-20s, cloud will push into the Red River Valley this evening. A shortwave tracking eastwards along the U.S. border will support area of showers or thunderstorms through the night. They will develop this afternoon in southern Saskatchewan and drift into southwest Manitoba tonight. The showers will reach Winnipeg through the second half of the night, but also be weakening as they approach. It’s unlikely that there’s enough “oomph” left by morning for there to be any thunderstorms; the Winnipeg area will see a few showers taper off early Saturday.
Skies will stay cloudy most of Saturday with a few sunny breaks possible in the afternoon. Temperatures will climb to around 20 °C, perhaps warmer if a bit more sun is able to peek out. More cloud will push in on Saturday evening as temperatures dip into the low teens.
The next disturbance will begin lifting northwards through the Dakotas on Saturday night. A broad area of showers and/or thunderstorms will develop across North Dakota on Saturday night and lift northwards. They’ll move into Manitoba early Sunday, and continue northwards through the day. Much of southern Manitoba will see showery conditions through Sunday with increasing humidity as the day progresses. While rainfall will be highly variable, it’s likely that much of the southern Manitoba will see 10–25 mm of rain through Sunday. Locally, depending on the strength of the convection, rainfall totals could reach 25–50 mm.
Temperatures will stay mild, though, with highs near 20 °C and a low on Sunday night in the mid-teens. Cloudy weather will continue on Monday with a chance for a few showers. Another disturbance is forecast to move through on Monday night which may bring more showers and thunderstorms to the region. With humid air in place, rainfall could be quite heavy. This will be a concern given the flood concerns that continue in parts of the province.
Long Range Outlook
Some more showers are possible Tuesday into Wednesday as yet another disturbance moves through the region. Cooler weather with with isolated to scattered showers will move in mid-week. The weather will finally stabilize for the end of the work week.
Today’s seasonal daytime high in Winnipeg is 22 °C while the seasonal overnight low is 8 °C.