Cold physics may bring heavier snow to eastern Missouri this weekend

An ABC 17 Stormtrack Weather Alert Day has been issued for Friday night and Saturday for the first snowfall of the season.

Snow totals in northeastern Missouri could reach 2 to 4 inches this weekend, with isolated higher amounts where snow persists the longest. A scenario for heavier snow is possible thanks to some cool, or rather cold, physics at play.

First, think of a cloud, which contains ice crystals, supercooled water droplets, and water vapor. This is water existing simultaneously as a solid, liquid, and gas. Most are familiar with condensation and evaporation, changing from solid to liquid or liquid to gas. But have you heard of sublimation?

Sublimation is the process of transitioning directly from a solid to a gas or vice versa, bypassing the liquid stage, and this happens all the time in clouds.

Water vapor can directly turn into ice as ice crystals grow in clouds, and ice can also evaporate into vapor under high winds and friction. These processes all require energy, which removes heat from the environment and cools the overall atmosphere. When precipitation rates increase and these processes happen more frequently, they cool the atmosphere even more.

This cooling may keep temperatures cold enough for snow to continue falling in eastern Missouri through late Saturday morning. In the high-end forecast, some areas could see totals above 4 inches, but this is mostly east of Mid-Missouri.

You should already have your holiday travel plans done before sunset on Friday, or consider staying off the roads on Saturday until roads clear later in the weekend.