Prairie Forecast: Building western ridge to bring warming trend

Last week’s weather forecast played out close to what the weather models were predicting. Western regions saw cooler-than-average temperatures move in, while eastern regions saw a brief return to summer-like temperatures.

This pattern was a response to an area of low pressure that spun up over the central U.S. during the second half of the forecast period. Warm air was pulled northward on the east side of the low, while cool air worked its way southward on the western side of the low. What was a little surprising was just how warm it got, with several regions in the warm sector seeing daytime highs in the mid- to even upper 20s. This warm air ended up combining with moisture streaming northward into the low, which helped to trigger several rounds of showers and some surprisingly strong thunderstorms. The low moved off to the east late on Tuesday bringing an end to the above average temperatures across Manitoba.

For this forecast period, it looks like we will see a bit of pattern reversal with eastern regions seeing several days of cool unsettled weather while western regions see a return of above average temperatures. The counterclockwise flow around the departing low over northwestern Ontario will help open the door for an area of high pressure to slide southeastward out of the Yukon. This high will bring below average temperatures to all but far western Alberta Wednesday and Thursday. Western regions will see sunny to partly cloudy skies while eastern regions will continue to see clouds and showers thanks to one last area of low pressure dropping southeastward ahead of the Yukon high.

By Friday the weather models show a ridge of high pressure building across the western Prairies as a large area of low pressure moves into the Gulf of Alaska. The rotation around the departing Yukon high and the Gulf low will help to build the ridge across the prairies bringing a return of dry warm fall weather to all regions by the Thanksgiving Day long weekend and into the first half of next week.

Alberta

This forecast period will start off with the Yukon high cutting across the province. This will bring a mix of sun and clouds along with the chance of showers to southwestern regions. Temperatures will be cool with daytime highs ranging from 7 to 12 C. Overnight low will be around the 0 C mark on both Thursday and Friday morning.

On Friday the flow will begin to switch to the south as a ridge of high pressure builds across the region. This ridge looks to build and strengthen right through the long weekend and into the first half of next week. Expect skies to be many sunny right across the province with daytime highs in warming back to around the 20 C mark by Friday or Saturday. There are some indications that southern and possibly central regions could see some mid- to even upper 20s on Sunday and Monday depending on just how strong the ridge gets.

Saskatchewan

For this region this forecast period will start off with plenty of clouds and showers on Wednesday and Thursday as an area of low pressure drops southeastward ahead of the Yukon high. This system should be through the province by Friday as the Yukon high moves through the region. This high will bring sunny to partly cloudy skies and cool temperatures with daytime highs on Thursday and Friday only expected to be in the 5 to 10 C range. Overnight lows also look to be cold with widespread frost forecasted on both Thursday and Friday morning.

By Saturday of the long weekend, this region will begin to feel the effect of the build ridge of high pressure over Alberta. Skies should become mainly sunny and daytime highs will warm back into the upper teens to low 20s. As the ridge builds over the weekend and begins to shift eastward, temperatures will continue to warm with widespread highs by Monday expected to be in the low 20s with overnight lows in the 4 to 8 C range. These dry and warm conditions are expected to last right through to at least Wednesday.

Manitoba

On Wednesday this region is still dealing with the moisture that is wrapping the departing area of low pressure that brought showers and thunderstorms too many regions on Tuesday. There may be a small break in the showers, mist and cloud cover late on Wednesday before more clouds and showers move back in on Thursday thanks to an area of low pressure sliding southeastwards ahead of the Yukon high. Temperatures will be cool with daytime highs expected to be in the 7 to 11 C range with overnight lows in the 2 to 4 C range, thanks to the cloud cover.

The building ridge of high pressure to the west looks as if it will take until Sunday or even Monday to be felt across this area. There will be the potential for frost from Friday to Sunday morning with the main controlling factor being cloud cover. Those areas that clear out will likely see frost with the potential for some killing frosts.

By Monday temperatures will begin to moderate, thanks to the building ridge of high pressure. Expect plenty of sunshine and warm fall weather to end this forecast period with daytime highs forecasted to be in the upper teens to around 20 C by Tuesday of next week.

— Daniel Bezte is a teacher by profession with a B.A. (Hon.) in geography, specializing in climatology from the University of Winnipeg. He operates a computerized weather station near Birds Hill Park, Man. Contact him via email with your questions and comments.