Don't come down on me hard, but I think this is climate change.
We've seen an unusual number of extreme jet stream patterns like this (massive ridges and troughs) in the past fifteen years, which happens to coincide with the period of time scientists have been observing record loss of summertime Arctic sea ice and record retreat of springtime snow cover in the Arctic. Scientists and myself wonder if it's possible that these changes in the Arctic are causing the wild jet stream behavior of recent years. If Arctic changes are truly to blame for the extreme jet stream behavior, losing the remaining 50% of Arctic sea-ice coverage between now and 2030 will bring even greater extremes. If the Arctic is not involved, that is worrisome as well, because that means jet stream changes are due to an unknown cause, leaving scientists with no idea how the jet stream will respond as climate change progresses. Therefore, my thoughts for the future years: expect the unprecedented.