Cooler nights means river valley fog for mid-Missouri

Cold fall mornings, similar to what mid-Missouri woke up to Thursday, is what residents along the river valleys will see daily, as well as fog. The fog at times can be quite dense as it hugs the valley and will burn off slowly during the morning hours.

If you were driving near the Route 54 and 63 interchange this morning, you likely came across this scene. MoDOT tweeted a picture Thursday morning of the dense conditions in Jefferson City near the Missouri River, as a layer of dense fog settled into the region. Elsewhere across the state, it was a seemingly quiet and sunny start to the day.

This is a picture from our traffic camera at the Route 54/63 interchange.

Somewhere…underneath all that fog…is Jefferson City.

If you travel in fog-prone areas this morning, use caution, keep the low beams on, and #BeSafe! pic.twitter.com/wVxs1m0STW

— MoDOT Central Dist (@MoDOT_Central) September 27, 2018

Fog develops all year, depending on certain factors that come together. However, fog can be more prevalent in the fall, especially for those near large bodies of water and in valleys. Fog most commonly develops overnight when the sky is clear, the air temperature is cooled to the dew point, and the wind is fairly calm. It usually sticks around for an hour or two after sun rises before dissipating, but valley fog can stick around longer.

So what is it, and why does it form most often during the fall months?

As the nights get longer, temperatures get cooler, and the warm rivers exchange some moisture with the colder air right above it, fog becomes a problem. Light winds above the ground at night allow for the fog to settle into the valleys.

In mid-Missouri, the water temperatures are still sitting in the mid 70s, and overnight lows are already falling into the upper 40s and lower 50s. This, along with the clear skies and recent rains, are the perfect recipe for valley fog to form each morning.

While it can be quite beautiful when viewed from bluffs, as the fog fills the valleys, it can be dangerous for those driving in the fog. It’s always important to remember when driving in fog to always use your low beams and be safe.

Since water cools off significantly slower than air, valley fog will be possible for quite some time. Stay with ABC 17 News as we continue to monitor the cooler weather and follow us on Twitter @ABC17Stormtrack.