Patchy dense fog has been present over Iowa these past few mornings. The featured chart presents a climatology of visibility reports from the Des Moines Airport being less than a mile by hour of the day and week of the year. While frequencies are small, the hours around sunrise this time of year have a slightly elevated frequency versus recent summer months. This time of year features increasingly longer nights allowing for more cooling and near surface moisture from mature vegetation that combine to allow temperatures to reach 100% humidity and fog to form. The decrease in wind speed as well also contributes as less mixing happens in the lower atmosphere.

Voting:
Good = 10
Bad = 0

Tags:   visibility