Behind the Forecast: How warmer weather can lead to more snowfall

Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.
Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.
Published: Dec. 2, 2022 at 9:16 AM EST
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LOUISVILLE, Ky. (WAVE) - There’s a misconception that a warmer climate would lead to less snow, but the opposite is true in many situations.

Two things are necessary for snowfall: sub-freezing temperatures and atmospheric moisture.

Warmer average winter temperatures have become the norm since the 1970s. Research has found that winter temperatures in the continental U.S. have warmed four-and-a-half times faster between 1970 and 2017 per decade than over the last century. Winter is now the fastest-warming season in most of the country. The number of days below freezing is expected to continue to drop over the next decades. For Louisville, the average winter temperature increased by 3.5°F between 1970 and 2018.

Warmer air can hold more moisture than cold air. In fact, for each additional degree rise (Fahrenheit) in temperature, air hold around four percent more water vapor. This increased moisture can lead to heavier rain and snowfall; it can also fuel more extreme weather events. The northeastern United States has seen the largest increase in heavy precipitation for any region in the U.S.; the heaviest precipitation events have increased by 50%.

Many regions of the world that can see snow are now dealing with more storms capable of holding and precipitating more moisture.

Since the atmosphere likes to be balanced, this also means that hotter and drier areas tend to get drier.

Warmer oceans can contribute to more winter weather in some locations. Our oceans absorb a considerable amount of the additional heat on our planet. In fact, they contain more heavy energy now than at any time during the last six decades. The moisture evaporated from oceans and seas is the perfect fuel for tropical systems and nor’easters.

The polar vortex is a band of strong westerly winds high in the stratosphere, between 10 and 30 miles up, over the Arctic. The strong winds of the polar vortex usually trap a large pool of intensely cold air. Warmer Arctic temperatures cause the polar vortex to weaken and stretch, allowing frigid Arctic air to dip south. When the cold Arctic air meets the warmer-than-normal water of the Atlantic off the east coast, dangerous nor’easters can form.

While a warming climate is leading to massive snowstorms in the winter for some, others have to deal with decreasing snowfall in the spring and fall. Fall snowfall (before December 1) decreased in every part of the country between 1970 to 2019, according to recent data. Spring snowfall (after March 1) dropped everywhere but the northeast and east-north central parts of the United States. Changes in winter snowfall varied across the United States. Southern states saw a drop in snow totals between 1970 and 2019, while north-central parts of the country saw an increase.

During this timeframe, Indiana and Kentucky saw decreasing snowfall totals during fall, winter, and spring. Overall, Louisville was one location that didn’t see much change in average seasonal snow trends. During the discussed timespan, Louisville only saw an average seasonal snowfall decrease of around an inch during the fall and winter. Our average seasonal snowfall in the spring increased by an inch. Nashville is dealing with a different situation. While they only saw slight decreases in fall and spring average seasonal snow totals, they now see eight inches less snow on average during the winter. Cincinnati has seen an additional four inches of average seasonal snowfall during the winter, while their fall and spring totals only decreased by around an inch.

Snow is a crucial part of our climate. It helps to cool the planet by reflecting sunlight back into the atmosphere. Snow also is a pivotal source of drinking water in the Western United States. Snow plays a significant role in our country’s agriculture; $47 billion in California agribusiness depends on the Sierra Nevada snowpack.