Patches of fog will clear by mid-morning.

上午十时左右，团团浓雾将散去。

《牛津词典》

There is also the possibility of some outbreaks of snow and sleet and a few freezing fog patches.

BBC: Northern Ireland

At the time of the crash there was low cloud, poor visibility and patches of freezing fog.

BBC: London helicopter crash: Crane work resumes on tower