The weather models did a really good job with the last forecast period. The upper ridge and associated surface high lingered over the eastern Prairies right through the long weekend. This brought some of the longest sustained heat of the summer.
Right on cue, the ridge broke down by Tuesday to make way for large upper low that brought cooler and unsettled weather. This upper low, combined with a building ridge over far western Canada, is what is going to drive our weather over most of this forecast period.
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We start this period with a large upper low over northern Ontario, an area of Arctic high pressure building southwards over Manitoba and strong but narrow upper ridge of high pressure over B.C. This particular setup is going to bring cool temperatures over the eastern Prairies for the next several days. Western regions will stay on the mild side.
An area of low pressure is forecasted to take an unusual path on Thursday—dropping nearly due south out of Nunavut and bringing rain to parts of southern Manitoba and southeast Saskatchewan. This low will then get caught up in the circulation of the northern Ontario upper low over the weekend, which will help to kick that low to the east.
Over Alberta and western Saskatchewan, weak upper ridging will give sunny to partly cloudy skies and warm early September temperatures.
The one tricky part to this forecast will be across the eastern half of Saskatchewan and western Manitoba. Cool air will flow southwards from Thursday to Saturday and, combined with clearing skies from the western upper ridge, could provide conditions that will allow for overnight temperatures to drop to near freezing values.
Alberta
Short and sweet forecast if you want warm and dry conditions. An upper ridge over B.C. is forecasted to expand eastwards during this forecast period. An area of low pressure dropping southwards into Manitoba on Thursday will drag a weak cold front across the northern half of the province to bring a mix of sun and the chance of a shower. Temperatures will cool down a little bit on Thursday and Friday as the upper ridge gets pushed back west.
Over the weekend and into the first half of next week, the weather models are showing the upper ridge rebuilding back to the east. This will allow skies to remain mostly sunny with daytime highs in the low twenties and overnight lows falling to around 12 C.
Saskatchewan and Manitoba
This is a bit of a messy forecast to start off. An upper low over northern Ontario is producing a northern flow across Manitoba and eastern Saskatchewan. An area of Arctic high pressure is quickly dropping southwards in the flow and bringing clearing skies on Wednesday.
This high will be quickly replaced by an area of low pressure forecasted to drop nearly due south out of Nunavut on Thursday. Precipitation from the low is forecasted to fall in a band from east-central Saskatchewan southeastwards into southern Manitoba. Temperatures under this northerly flow will be cool with daytime highs forecasted to be in the low teens and overnight lows around the 5 C range.
This low will quickly pull off to the east on Friday, which will allow for clearing skies over Saskatchewan by Thursday night and by Friday afternoon across Manitoba. The clearing skies and cool air mass will set the stage for some possible frost over central and eastern Saskatchewan overnight Thursday and Friday. Western Manitoba could see some light frost on Friday and Saturday morning.
Clear skies and warming temperatures are expected over the weekend and into the early part of next week as weak upper ridging builds in and the flow across the region becomes more southerly. Expect daytime highs to warm back towards the twenty-degree mark with overnight lows falling to around 10 C.
