Calgary Weather: City Under Heat Warning

As expected, the heat warnings have been expanded to include Calgary.

And Lethbridge.

Daytime temperatures in Calgary are expected to be five to eight degrees above the seasonal average, while daily minimum temperatures are expected to be four to seven degrees below average.

Environment and Climate Change Canada (ECCC) issues heat warnings for most of Alberta when daily maximum temperatures are expected to be at least 29°C, with daily minimum temperatures of at least 14°C for at least two consecutive days (ECCC’s threshold is slightly higher in the province’s southern regions, including Medicine Hat, Pincher Creek and Lethbridge).

This warm, dry weather is the result of a high pressure system that starts off the west coast of the US and extends into central Alberta.

There are some notable differences between this heat wave and the one that hit the western Prairies for much of July.

This system is not anchored, which allows the meridional flow in the upper layers to resume instead of remaining stationary. Furthermore, this ridge does not extend as far north as the record mountain from earlier this month.

Convective activity is expected along the northern edges of the ridge, resulting in severe thunderstorms. Both warnings and advisories were issued Wednesday afternoon.

These storms move quickly across the country and the biggest threats are strong winds and large hailstones.

There is a chance of more thunderstorm activity on Thursday, with a few cells possibly moving east from the hills. At the moment, however, the chance of this is quite small for this region.

Since this ridge is not expected to remain on the west side, instability will increase as it collapses. This will cause temperatures to drop to closer to seasonal levels, but there will also be some showers and thunderstorms towards the end of the long weekend.

Calgary could see 12 to 18 millimeters of rain from Sunday to Tuesday. Early next week, daytime highs of around 20 degrees are expected.