The final weekend of June is shaping up to be a wet one for Calgary. A rare ‘Rex Block’ weather pattern is moving in, which is when a high-pressure system is positioned directly north of a low-pressure system. When this type of blocking formation occurs, the two associated weather patterns feed into each other, causing them to linger over a given area for several days to weeks at a time. The last notable Rex Block in Alberta was back in 2013 and was a primary force in the extreme flooding Calgary experienced. Yellow and orange level rainfall warnings are in place this weekend for the Edmonton area and regions southeast of the capital, while heat warnings are in place for the extreme north and severe storm watches are in effect for the Calgary area. The Rex Block will be most impactful for Calgary on Sunday into Monday with heavy rain and strong winds up to 50-70 km/h from the northwest. Models are predicting rainfall amounts from 20-50 mm throughout southern Alberta between now and Monday morning. It’s important to note though that even a slight change to this weather pattern can significantly impact rainfall amounts, for better or for worse. Weather models typically update every one to four hours and can fluctuate quite a bit between updates. They are a great tool to monitor what could be coming, but they are not a crystal ball. That being said, it seems pretty certain we are in for a cool conclusion to June and even the first couple of days of July as well!
