Insider Blog: Where did Monday morning’s fog come from, and what made it dangerous?
Early Monday morning, drivers were treated to an intense bout of fog in some areas.
Missouri State Highway Patrol's Troop F tweeted this photo of I-70 in Callaway County, showing visibility at less than one tenth of a mile.
This image from MODOT's South Rocheport Bridge camera over the Missouri River, shows visibility perhaps even lower.
Several communities across mid-Missouri saw morning commutes threatened by fog, especially as air temperatures were below freezing. This created the dangerous potential for freezing fog which can form a glaze of ice on any surface also below freezing.
The happening could potentially be explained as advection fog. With a weak changeover to a south wind in some of the areas reporting fog, it's possible that a relatively warm airmass was advecting, or being blown over a cold airmass already in place.
This is called advection fog and can happen a lot in the winter. Thanks to existing snow pack, the ground is very cold. If winds stay calm, the cold snow pack can cause warmer air moving in overhead to cool to it's dewpoint and condense into fog.
We will have to monitor the forecast for more events like this as long as we have relatively calm winds, and a contrast between warm moist air over an existing cold snow pack.
