The National Weather Service has a Dense Fog Advisory active for portions of north central Iowa this morning, which includes Cerro Gordo County (Mason City). The featured plot presents the distribution of advisory duration for this event type and county location. The orange line presents the duration of the advisory at issuance and the blue line represents the final duration after any extensions and/or early cancellations. Sometimes the initial advisory is expanded in time, so why the blue line is sometimes higher than the orange line. Anyway, the present advisory extends seven hours, which is right at the 50% level for frequency, which implies approximately the median value. These events tend to be limited to peak overnight cooling hours as the air temperature cools to the dew point and then "burn off" with the rising of the sun causing an increase in temperature away from the dew point.

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Tags:   densefog