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How snow can impact the next day’s temperatures

When people think about snow, most think that it doesn’t do anything to the environment after falling. But in reality, new snow on the ground can impact the next day temperatures, and if it’s sunny out after a fresh snowfall, an interesting feature occurs.

Post-Snowfall Temperatures
It comes as no surprise that snow, is, well… cold. Snow is ice after all, and that means that it is at 32ºF. That’s cold! So on a day when temperatures are expected to be warmer than the ground, the snow could actually lower the surface temperatures. An example is what we saw Sunday for our high temperature in Muncie.
Before this snow-tacular event that occured Friday, it looked like temps would be in the lower 40s on Sunday. But as the event went on, and the totals overperformed, plenty of snow was layered on the ground heading into Sunday. Temps to start of the day were in the mid-teens! But throughout the day, temps only got into the mid-30s for its peak, instead of the expected lower 40s.
Imagine having a glass of ice water and a glass of water (Figure 1). Typically, the glass of ice water is colder, and stays colder for a longer time when compared to the glass of water without ice. This is the same for snow and air. If a measurable amount of snow is on the ground, then it can contribute to colder air, and keep the air just a little bit cooler for a longer time.

Figure 1

Reflection and Albedo
If you ever wonder why it seems brighter outside when fresh snow is on the ground? This is from a reflection resulting in the snow’s albedo. But what is albedo, and how would that impact temperatures? In our case, albedo is the amount of sunlight reflected by an object to the amount incident to it. The greater the albedo fraction/decimal, the higher the amount it reflect. The higher albedos tend to have a white color, as white colors indicate that they only reflect all visible light. Lower albedo indicate darker colors, with black as the “perfect” absorber of visible light. Fresh snow, as white as it is, has a very high albedo, especially for a natural source. Its albedo is 0.80, which is very high. This means it is reflecting a lot of visible light, while absorbing a little light in. This is why on snowy nights or sunny days, it looks a lot brighter than usual. Sometimes sunglasses aren’t quite enough to keep you from squinting on a sunny snow-day. The snow becomes a “mirror” of light so to speak.
The question still remains, though, of how albedo would affect temperature? Well, if snow is covering the ground, most solar radiation that would come in would bounce off of the snow and back into the atmosphere. The surface, and for that matter, most of the atmosphere does not absorb the solar radiation that is bounced back by the snow, so the snowy surface only sees some warming with the small amount of absorbed radiation. If the ground did not have snow, it would be absorbing incoming solar radiation and releasing infrared energy, which can heat the surface air a little bit. But if the snow is on the ground, it can block both incoming shortwave radiation (the sun’s radiation), and outgoing longwave radiation (the ground).

So whenever you see fresh snow on the ground, and the next day is sunny, grab those sunglasses for sure! And on some sunny days after a previous days’ snowfall, temps might be a bit more contained from the snow on the ground.

-CWS Forecaster Lance Huffman

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