Daytime highs will sit in the mid- to high 20s to the low 30s across Alberta on Tuesday. The main weather-maker is a ridge of high pressure situated over the western provinces, so stable weather conditions will prevail. A potent low-pressure system in the north Pacific basin will slide into British Columbia on Tuesday and introduce some precipitation and initiate a period of instability heading into the long weekend. Rain is likely over central and southern B.C. on Tuesday, and that precipitation will cross over the central Rockies overnight. That same system is expected to re-enter southern Alberta via Montana on Wednesday afternoon with rapidly developing thunderstorms likely in the southwest corner of the province. The counter-clockwise rotation around that low will force persistent rain against the eastern slopes of the foothills, and by Friday some areas could see notable accumulations. These synoptic setups make it very difficult to forecast pinpoint locations of precipitation and/or totals until the low has entered the leeward side of the range. Calgary could see some rain on Wednesday but is more likely to see higher totals on Friday night. The Labour Day forecast includes daytime highs in Calgary that will sit at or below the average value of 20 C. It will likely be cloudy in Calgary for the bulk of the weekend with intermittent rain showers from Friday until Tuesday.
