Calgary weather: Fog and freezing drizzle to start the new year

Intense and persistent fog developed over southern Alberta on Thursday and continued Friday morning.

Early Friday Environment and Climate Change Canada (ECCC) issued freezing rain warnings for communities in central Alberta – including Red Deer, as well as extensive fog advisories for the southeast corner of the province.

As of 9:30 a.m. a yellow warning fog advisory remained across most of southern Alberta – including Calgary, Lethbridge, Red Deer, and Medicine Hat, with the national weather agency explaining,

“Areas of dense fog continue. Visibility is expected to improve by this afternoon, but foggy conditions will return tonight then persist until Saturday afternoon. There is also a risk of freezing drizzle.”

Throughout the morning commute Friday visibility in Calgary and on area highways was severely limited. Ice appeared to accrue on some 511 Alberta cameras in central and southeastern Alberta including near Red Deer and Brooks.

Not unusual

Fog is not unusual across this region of the country, but when fog does form here it tends to be short-lived due to surface winds and a predictable warmup after sunrise.

Thus the fog that usually forms around southern Alberta will mix out once there is an infusion of heat (initiated by incoming solar radiation aka the sun warming the Earth’s surface) and/or due to stronger wind speeds.

The fog that developed Thursday is proving to be unusually persistent because of an atypical synoptic set-up. Normally there is a distinct west to east pattern along the jet stream, and stronger westerly winds are common. Right now there is an upsloping flow in southern Alberta (weather moving east to west vs west to east) and that, plus the topographical barrier of the Rockies west of Calgary - has allowed fog to form and remain in place closer to the surface.

Friday is going to bring only mild wind to the region without a significant change in temperature, so fog is expected to persist throughout the day Friday and again on Saturday.

Cold Arctic air will continue to funnel into the northernmost regions producing cold wind chill values and more snow is likely in northern Alberta, B.C., and Saskatchewan to start the weekend.

Daytime highs in Calgary will peak between -5 C and -9 C from Friday until Sunday with a gradual warmup after that.

More snow is likely in the B.C. interior and the western slopes of the Rockies on Saturday – but the bulk of precipitation will fall west of the Highway 2 corridor.

Calgary could see some freezing drizzle on Friday but as of 10:30 a.m. Friday the greater concern is compromised visibility due to fog.