Persistent precipitation has fallen west of Edmonton with nearly 60 millimetres of rain recorded between Hinton and Grande Prairie as of Friday morning. A rain-wrapped low-pressure system has been situated east of the northern Alberta-B.C. border, and more rain is expected in that area for the start of Friday. As of 7:30 a.m. Friday, a yellow-level rainfall warning was still in place, with Environment and Climate Change Canada explaining, “An additional 10-25 mm is expected today before the system weakens this evening.” Special weather statements were issued for southeastern B.C. north of the TransCanada Highway, and communities west of the northern Rockies. The national weather agency advised, “Prolonged periods of moderate to heavy rain are expected,” anticipating between 40 to 60 millimetres by Friday night. “Water will likely pool on roads and in low-lying areas. Some travel delays are possible. Watch for washouts near rivers, creeks, and culverts. Increased risk of landslides in vulnerable areas such as steep slopes, deforested areas or recent burn scars.” Thunderstorms are possible throughout the day across much of northern Alberta before that low moves into Saskatchewan. A second low-pressure system from the Pacific basin is expected to track south and east over the weekend becoming the main weather-maker for central and southern Alberta. This low will pick up moisture from the Pacific and drop it over southern B.C. and Alberta. Two anchoring high-pressure systems will hold that low in place and allow instability to prevail until early next week. Daytime highs will sit below seasonal for most of the west – including in Calgary. Overnight lows will remain above seasonal and sit closer to the daytime highs for the weekend – but the most noticeable component to the weekend forecast will be the conditions. Cloud cover is expected to dominate, and scattered showers are likely along the foothills on Friday. Isolated thunderstorms are possible on Saturday, with intense rain starting Sunday. Moderate to severe thunderstorms are possible east of the QEII and Highway 2 on Sunday and Monday. The forecast rainfall totals for Calgary are trending down from Thursday’s models – but there may still be some localized flooding in areas with poor drainage or at the base of slopes as some surfaces could become saturated. Daytime highs in Calgary will return to the low-20s by the middle of next week. The average high this time of year is 20 C with a low of 6 C.
