Quick cool spell to end the month before highs near 10 C

A brief blast of Arctic air will spill across Alberta Thursday, holding daytime highs below freezing for much of southern Alberta.

This comes on the heels of an unusually warm November, making Thursday the only day of the month with a high at or below 0 C.

As mentioned yesterday, Calgary’s average daytime high for November ranges from 7 C to 0 C, but it is not uncommon to see days that are colder than that. According to the Canadian Climate Normals data from Environment and Climate Change Canada, Calgary typically experiences 8.4 days in November with a daytime high at or below freezing.

This cool down can be traced back to a persistent and dominant broad upper low sitting over Hudson Bay coupled with ridging extending from British Columbia to the Yukon. There is a similar setup at the surface, and in between the ridge and trough sits a baroclinic zone – with stronger winds moving colder air across the Prairies.

That eastern low will start to track north and east on Friday making room for the ridge to the west, to edge further into B.C. This aligns with another spike in daytime highs for Calgary as warmer air will settle over southern Alberta.

More ridging early next week will produce a daytime high in Calgary of at least 10 C by Tuesday - which will be around 12 C above seasonal.

The overnight lows Thursday and Friday will still be above a seasonal -11 C, and from Monday through Wednesday the overnight lows are forecast to be warmer than the average daytime highs.