21.   First, San Francisco Airport is chronically congested, and prone to heavy fog.

22.   Heavy fog generally rolls into the area each evening, and firefighters count on it to help extinguish flames along the coast.

23.   Heavy fog hung over the settlement, producing a lull in the shelling and artillery fire that had raged long into the previous night.

24.   Heavy fog, which limits visibility to a quarter of a mile or less, occurs, on average, less than two days per year around Phoenix.

25.   Heavy fog sometimes reduces visibility so much that the channel has to be closed.

26.   Heavy fog disrupted air traffic at the three major airports in the New York City area on Thursday, the Port Authority of New York and New Jersey said.

27.   Just last week, a heavy fog rolled over LAX, forcing controllers to slow the pace of landings and departures significantly.

28.   Moreover, heavy fog is usually not observed in April, given declining moisture in desert soils.

29.   On Friday as the heavy fog cover grew patchy, the shooting began.

30.   On our way back, heavy fog quilted both the alders and a range of spectacular mountains, the Fairweathers, that line the bay.