Daytime highs will remain in the mid-to-high 20s on Friday across central and southern Alberta, but that will be the warmest day for at least a week. A shift in the upper pattern will bring cooler air and intense rain for portions of the province with some areas in northern Alberta expecting over 60-millimetres of rain to start the weekend. There is some disagreement with the forecast models, but it’s possible some areas near High Level will record close to 100-millimetres of rain by Saturday morning. Yellow-level rainfall warnings have been issued for the northwest portion of the province with Environment and Climate Change Canada explaining the rainfall totals will be highly variable with this system and, “Water will likely pool on roads and in low-lying areas. Some travel delays are possible.” On Saturday, a low-pressure system will cross over the Rockies west of the QEII and produce isolated showers and thunderstorms. There is a chance of rapid intensification along the northern edge of this low and some cells may develop into moderate to severe thunderstorms west and south of Edmonton by Saturday night. Calgary may experience brief periods of scattered showers and/or thunderstorms on Saturday night, but the more notable change will be stronger north winds to kick off a cooldown. On Sunday, more persistent rain is forecast for the east-central corridor of Alberta with higher rainfall accumulations likely east of the QEII Highway. Depending on where this low-pressure sets up and how it moves across the prairies, Calgary could see rainfall totals over 10 millimetres from Sunday to Monday, or the city might sit just west of the worst of it. Daytime highs will return to the low 20s to start next week with a mix of sun and cloud. The long-range forecast shows a trend toward below seasonal highs and potentially cloudy and/or rainy conditions for the start of the Labour Day long weekend.
