How snow cover can lead to cooler overnight temperatures

It's no secret the last couple of weeks have seen exceptionally cold nights. Even more recent, lows have dropped to the single digits. A strong arctic air mass holds most of the blame for this cool spell, but recent snow cover has led to a slight dip in overnight temperatures compared to nights without the snow cover. This is due to the increased albedo of snowfall during the daytime hours.

Albedo is the measure of reflectivity with light. The darker the color, the less reflective a surface is and the more energy in the form of heat is absorbed into the object hit by the sunlight. Fresh snow can seen an albedo of up to 90% meaning the earth's surface in that region covered is sent back out into space during the daylight hours.

Much of the northern half of Mid-Missouri has seen a considerable amount of snow cover from last weekends winter storm. Whenever there is less heating of the earth's surface during the daylight hours caused by sunlight, there is less heat to radiate from the earth's surface during the overnight hours causing cooler lows.

An example from this event is show by Thursday night's surface road temperatures. Areas with less snow cover see a degree or two decrease from those areas not covered by snow.

With additional snowfall expected lasting from Thursday night through Friday at noon, areas that saw mostly ice during the previous winter storm will see increased totals than areas further north. This means most of Mid-Missouri will look to remain completely covered heading into the weekend leading to cooler temperatures overnight than with no snow cover.