Last week, News5 viewer and frequent photo contributor Bonnie Sumner sent in a photo with a question: Is this fog?The answer is yes, and it's a unique example of a weather phenomenon called upslope fog.Sumner's photo shows a clo ud extending away from a mountain and sitting clearly above the ground. While it may not look like the fog most people picture, the science behind it confirms it qualifies.How upslope fog formsUpslope fog begins with relatively cold air located low on the slopes of a mountain. Wind pushes that cold air up the mountain, where it gets even colder. As the air cools, its relative humidity increases. Eventually, the air cools to the point of saturation and the water condenses into a cloud fog.How radiation fog formsThe fog seen along I-25 this week is a different type called radiation fog, though this week's situation is a hybrid because upslope flow also contributed.Radiation fog forms when there is a layer of low-level moisture near the ground and heat escapes upward through that layer. As the moisture rises and the air cools, the air saturates and fog forms, with the moisture trapped beneath the warmer air above.Both types of fog have been responsible for the foggy conditions residents along I-25 and the eastern plains have experienced multiple days this week.If you have a weather question, send me an email: [email protected]____Have a question or story idea you would like the First Alert 5 Weather team to consider? Email: [email protected] KOAA News5 on your time, anytime with our free streaming app available for your Roku, FireTV, AppleTV and Android TV. Just search KOAA News5, download and start watching. ...read more read less