Edmonton fog lasted all day Sunday, an unusual event that grounded flights

Fog hung over Edmonton all day Sunday and did not clear until later that night, with visibility near one-eighth of a mile for much of the day and close to zero between 11 a.m. and noon. Environment Canada meteorologist Matt Albers told the Edmonton Journal that the city is not used to fog lasting that long.

Albers said snow that fell Wednesday and Thursday evaporated after temperatures warmed on Halloween. Overnight ground cooling under warmer air aloft formed what he called "a lid or cap" that trapped moisture, while slow easterly winds and a shallow autumn sun failed to break it up. "Typically, our sun is strong enough that it can warm up the ground, remove that lid at the surface, and help to mix out the moisture to get rid of the fog," he said.

Edmonton International Airport reported 36 flight cancellations and delays Sunday because of fog and 13 cancellations Monday. Conditions improved from around 9 a.m. Monday and operations were returning to normal. Albers advised commuters to use headlights and slow down. "Ultimately, if anything isn't overly important for you to do that day, maybe reschedule plans," he said.

Forecast highs this week are 7 to 11 degrees Celsius, warmer than average for the time of year but within the normal range for the city, Albers said, because a jet stream shift is pulling warm air north from Montana. Snow machines are running at Snow Valley and Rabbit Hill, though neither hill is expected to open until later in the month.