A very stable weather pattern has set up across the western prairies, bringing consistently warm temperatures. Daytime highs in Calgary will range from 20 C to 25 C from Thursday until next Friday, with overnight lows between 7 C and 9 C. The normal range in Calgary this time of year is 17 C for a high and 4 C for a low. Zonal flow across the southern half of B.C. and Alberta will allow Pacific air to travel west to east toward Saskatchewan. A series of low-pressure systems to the north and a closing low south of British Columbia will keep this pattern steady well into next week - meaning there is no threat of instability and little to no cloud cover expected until after the weekend. Rural areas — especially those with a lot of open vegetation — may experience a risk of frost some mornings or fog. The frost would develop from the lack of an insulating layer (cloud cover) that traps heat closer to the surface during the typical nocturnal release of outgoing longwave radiation from the surface. Fog may develop in areas where there are slightly lower overnight values, both rural and urban, but especially low-lying areas or places near bodies of water and/or with vegetation.
