Here's how a wavy jet stream is screwing up weather all over the US this weekend

The jet stream is fueled by the difference in temperature between the arctic and the area south of it. Global warming is warming the arctic much faster than the more southern areas, so there is less temperature difference, thus less energy to run the jet stream. This allows it to weaken more often, causing the waviness that allows the polar vortex to escape south.

https://www.livescience.com/extreme-may-weather-polar-vortex.html

By Rafi Letzter
May 9, 2020

Temperatures are expected to drop to record lows for this time of year across much of the northern U.S east of the Rocky Mountains. The culprit? A low-pressure mass of Arctic air is making its way down through Ontario, Canada, according to the National Weather Service (NWS).

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The air mass making its way south is part of what's often called the "polar vortex," a swirl of frigid air usually confined to the Arctic by the circulating atmospheric current known as the jet stream. Sometimes, wobbles in the jet stream allow some of that Arctic air to escape south, according to the NWS.

A National Oceanic and Atmospheric Administration graphic shows how disturbances to the jet stream produce extreme weather.

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The relationship between polar vortex escapes like this and climate change isn't yet fully understood, but many studies (summarized in this paper published in the journal Science Advances in 2018) have found climate change effects can disturb the jet stream and lead to extreme weather events.

The Weather Channel reported that this weekend should see multiple low-temperature and possibly low-pressure records fall. Meanwhile, a high-pressure block of lower-latitude air "bulging" northward to the west should bring extreme heat to the other side of the Rocky Mountains.

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