September 27th, 2019

// Weekend Blizzard Set to Bring Historic Snowfall to the Northern Rockies

Weekend Blizzard Set to Bring Historic Snowfall to the Northern Rockies

Wavy jet stream consistent with climate change

An early-season snowstorm could bring up to 4 feet of snow in the Northern Rockies. The heaviest snow and most extreme conditions are forecast to happen on Saturday and Sunday, and Winter Storm Watches have been issued across portions of Montana. Such a storm has not occurred in the northwestern part of the state since 1934

Record-setting September snowfall isn’t what most people think of when they imagine climate change, but there’s a reason scientists prefer the term “climate change” to “global warming.” Global warming describes the average global surface temperature increase from human emissions of greenhouse gases. Global warming causes climate change, a long-term change in a region’s climate, and the change isn’t always what one might expect.

Climate change is making extreme cold events less likely on average, but it is also increasing the frequency of extreme precipitation, and destabilizing the jet stream. The result is that certain areas and seasons are getting a lot more blizzard weather, and in other areas, blizzards are less common. The forecasted blizzard is the result of a wavy jet stream pattern. 

Here are the climate change signals related to the current storm:

Climate change destabilizes the jet stream.

The Arctic is warming much faster than areas farther south, which reduces the temperature difference between the two regions. Because that temperature difference provides the main fuel for the polar jet stream (a river of strong wind at levels where jet aircraft fly), the jet stream weakens and favors a more meandering north-south path.

The blizzard headed for Montana is due to a wavy jet stream pattern responsible for “record-challenging heat in the East” and “dramatically cooler conditions in the West.”

Climate change increases the frequency of extreme storms.

Warmer air holds more moisture and causes more intense rain and snow storms. NOAA scientists, examining 120 years of data, found that there were twice as many extreme regional snowstorms in the US between 1961 and 2010 compared to 1900 to 1960.

Early autumn extreme snowfall events are less likely.

On average, climate models suggest that early autumn extreme snowfall events in the Northern Great Plains are less likely due to human-caused climate change. This average trend, however, does not preclude extreme weather outbreaks tied to Arctic warming and a destabilized jet stream. These outbreaks of Arctic air can break cold temperature and snowfall records even as the average temperature increases.

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